Sequential Prophet-5 MIDI User manual

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OPERATION
MANUAL
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MODEL 1000
Revision 3.3
S/N l^06i^ up
Manual No. CMIOOOD
PROPHET-5 SYNTHESIZER
Oi>ERATION MANUAL
By
STANLEY]UNGLEIB
Sequential Circuits, tie.
3051 North 1st Street
San 3ose, CA 95 13^^
(i^OS) 9^6-5240
TELEX: 36^^12 INTR

PROPHET-5 SYNTHESIZER
OPERATION MANUAL
By Stanley 3ungleib
Revision 3.3
S/N 406^ up
Manual No. CMIOOOD
Issued: February, 1982
Copyright©1982 by
SEQUENTIAL CIRCUITS, INC.
All rights reserved. Printed in USA.
The contents of this manual are the property
of SCI and are not to be copied or reproduced
without our prior written permission.
11

About the Prophet-5
The Prophet-5 has been the world's leading polyphonic keyboard synthesizer since its
appearance in January, 1978. Renowned among professionals for the range and quality
of its sound, it provides five-voice capability and now allows the keyboardist to
instantly select from 120 sounds (programs). All programs can be fully customized
(edited) and stored internally, or on audio tape via the built-in cassette interface.
The Prophet-5 actually contains five individual synthesizers, termed 'Voices." For its
principle sound sources, each voice contains two voltage-controlled oscillators (VCOs),
referred to as OSC Aand OSC B. OSC A, OSC B, and a white noise source can be
mixed into aresonant low-pass voltage-controlled filter (VCF). The filter modifies the
voice timbre under control of its four-stage envelope generator. The filter may also
serve as asound source. Following each filter, avoltage-controlled amplifier (VGA)
also controlled by afour-stage envelope generator shapes the voice amplitude. Only
one voice is depicted on the control panel, because the voice controls "patch" the five
voices identically. This makes the voices homophonous—they sound alike—with pitch
differences corresponding to (at most) five simultaneously-held keys.
Supplementing the basic voice are polyphonic modulation (POLY-MOD) signal routings
within each voice that allow OSC Band the filter envelope generator to function as
modulation sources applied to OSC Afrequency or pulse-width, or to the filter
frequency. Finally, there is asingle low-frequency oscillator (LFO) and apink noise
source which can be mixed to modulate all five voices, as adjusted by the modulation
(MOD) wheel. The PITCH wheel raises or lowers the pitch of all voices by the same
interval.
The term "digital-analog hybrid" is often used to describe the Prophet. This means that
instead of directly controlling the analog synthesizer voices, the keyboard and most
controls are actually devices which input "data" to amicrocomputer system which in
turn "programs" the voices. The microcomputer system has three main functions.
First, it solves the problem of generating five independent sets of voice control
voltages and gate signals (which operate the envelope generators) from asingle
keyboard. Second, its digital memory provides away to store all of the switch and
knob settings which form aprogram. These programs are retained by the microcompu-
ter's memory even when the Prophet is turned off, thanks to asmall battery with a10-
year life. Third, the microcomputer system keeps the ten voice oscillators in tune.
Accessories specifically designed for the Prophet-5 include the Model 1005 Polyphonic
Sequencer which allows direct storage of lengthy keyboard sequences, and the Model
1001 Remote Keyboard. For increased performance flexibility, the Model 8'>2 Analog
Interface Adapter enables remote control of the PITCH and MOD wheels by two Model
St^O Voltage Pedals.
Congratulations on choosing the Prophet-5. It has already become aclassic.
1X1

Table of Contents
About the Prophet-5
SECTION 1BASIC OPERATION
1-0
1-1
1-2
1-3
1-*
1-5
1-6
1-7
1-8
1-9
INTRODUCTION
SET-UP
POWER-ON AND INITIAL TUNING
PRESET SELECTION
PITCH AND MOD WHEELS
RELEASE FOOTSWITCH
RETUNING
VOICE ASSIGNMENT
VOICE DEFEAT
EDITING AND RECORDING PROGRAMS
111
1-1
1-1
1-2
1-3
1-3
1-4
1-4
1-4
1-4
1-5
SECTION 2FRONT PANEL
2-0 INTRODUCTION 2-1
2-1 MODES OF OPERATION 2-1
2-2 VOICE SIGNAL FLOW 2-2
2-3 OSCILLATOR A2-4
2-4 OSCILLATOR B2-5
2-5 MIXER 2-6
2-6 FILTER 2-6
2-7 AMPLIFIER 2-8
2-8 MISCELLANEOUS 2-9
2-9 MODULATION 2-9
SECTION 3BACK PANEL
3-0 INTRODUCTION 3-1
3-1 AMPLIFIER CONTROL VOLTAGE IN 3-1
3-2 FILTER CONTROL VOLTAGE IN 3-1
3-3 MONOPHONIC SEQUENCER INTERFACE 3-1
3-4 ANALOG 3-2
3-5 DIGITAL 3-3
SECTION 4CASSETTE INTERFACE
4-0 INTRODUCTION 4-1
4-1 FUNCTION 4-1
4-2 RECORDER AND TAPE SELECTION 4-2
4-3 CONNECTIONS 4-2
4-4 RECORD AND PLAYBACK LEVELS 4-2
4-5 PRECAUTIONS 4-3
4-6 SAVING TO TAPE 4-3
4-7 LOADING FROM TAPE 4-3
4-8 PROBLEMS 4-4
iv '. CMIOOOD 2/82

SECTION 5SCALE MODE
5-0
5-1
5-2
INTRODUCTION
KEYBOARD INTONATION
USE
5-1
5-1
5-2
SECTION 6SYSTEM INTERFACE PROGRAMMING
6-0
6-1
6-2
6-3
6-4
6-5
6-6
6-7
6-8
6-9
6-10
6-11
6-12
6-13
6-14
6-15
6-16
INTRODUCTION 6-1
DATA FORMAT 6-2
ERROR CHECKING 6-2
STATUS BYTES 6-3
STATUS 0: SEND KEYBOARD/PROGRAM 6-3
STATUS 1: RECEIVE KEYBOARD/PROGRAM 6-4
STATUS 2: TRANSPOSE ON 6-5
STATUS 3: SAVE TO TAPE 6-5
STATUS 4: LOAD FROM TAPE 6-6
STATUS 5: CLEAR TRANSPOSE 6-6
STATUS 6: INITIALIZE SEQ LOWER PROGRAM 6-6
STATUS 9: DISABLE TUNE 6-7
STATUS A: ENABLE TUNE 6-7
STATUS B: RECEIVE PROGRAM CHANGE 6-7
STATUS C: SYSTEM CONNECT 6-7
STATUS E: RECEIVE SHORT KEYBOARD DATA 6-7
STATUS 80: START TUNE 6-7
SECTION 7SELECTED BIBLIOGRAPHY 7-1
SECTION 8FACTORY PROGRAMS
8-0
8-1
8-2
INTRODUCTION
PROGRAM FILE 1
PROGRAM FILES 2AND 3
FILE 1PROGRAM MAP
FILE 2PROGRAM MAP
FILE 3PROGRAM MAP
FILE 1PROGRAM DIAGRAMS
8-1
8-1
8-2
8-3
8-4
8-5
8-6
SECTION 9PANEL BLANKS 9-1
CMIOOOD 2/82

SECTION 1
BASIC OPERATION
1-0 INTRODUCTION
This section contains instructions for set-up and basic operation. After unpacking, read
paragraph 1-1 and connect the Prophet-5 as described. The remaining paragraphs in
this section cover tuning, program selection, and other essential information.
The Prophet-5 offers astounding sonic flexibility and performance. To exploit these
capabilities fully, learn as much as you can about it with this manual and the books
listed in the bibliography (Section 7). Additional references can be obtained from the
more extensive bibliographies contained in the sources listed. Thus prepared, you will
no doubt create many interesting sounds. Be advised that in the excitement of creation
patches tend to escape if not documented. Panel blanks for this purpose are provided
at the back of the manual.
Remember the Prophet-5 is asophisticated device. It should be handled with as much
care as you would afford an acoustic instrument. Shock or vibration can damage the
keyboard or controls, and can loosen socketed integrated circuits (ICs). Avoid
temperature extremes. If you expect to transport the Prophet-5 regularly, we urge you
to invest in aprofessional "road" case for it. These are made by several manufacturers
and should be carried by your music dealer. If you can't find acase, please contact the
SCI Sales Department.
1-1 SET-UP
The Prophet has aswitch on its back panel for selecting between a115- or 230-Vac
power source. Prophets shipped in the U.S. and to Japan are usually switched to 115V,
and those destined for Europe are usually switched to 230V. CAUTION: Check this
switch and set to match your line voltage before plugging in the instrument. Don't
change this switch when the line cord is connected. If you do switch the line voltage
selector, you will have to change the fuse also. Use 3AA SLS"-BL0 for 115V and 1/2
A
SLO-BLO for 230V.
As does most electronic equipment, the Prophet comes with athree-prong power plug
to insure safe grounding with other equipment. The ground prong is connected to the
metal chassis of the instrument. It is up to you to check the ground connections of the
Prophet and all other instruments and equipment you use to prevent potentially lethal
shocks. As you probably know, many older buildings and clubs are notorious for their
poor quality AC wiring. We therefore urge you to use one of the several "ground-
checking" devices available on the market to verify AC connections.
CMIOOOD 2/82 1-1

Because of the AC ground, a"ground loop" will often be created when the audio cable
is connected between the Prophet and its amplifier. As aresult, low-level hum may
occur. Defeating the AC ground with atwo-prong adapter will usually defeat the hum,
but this practice can also set up ashock hazard between the units. The hum level will
depend on exactly how the two units are connected to the AC. For minimal hum, use
the same outlet for both the Prophet and its amplifier. This should reduce the hum to
an acceptable level.
In short, we recommend the following steps when connecting the Prophet-5:
1. Plug the Prophet into athree-prong outlet. Don't defeat the AC-ground.
2. Plug all other equipment such as amplifiers, volume pedals, and effects devices into
the same outlet. WARNING: Do not overload. When in doubt, consult an electrician.
3. Verify all equipment grounding with aground tester.
WARNING: Sequential Circuits, Inc. is not responsible for any equipment failure due to
incorrect AC power connections, and is not liable for any personal Injury <hie to
electrical shocks as aresult of poor grounding.
This is an excellent time to think about your amplifier and speaker system. By
converting the synthesizer's electrical output into the potent vibrations you hear, your
sound system becomes part of the instrument. Of course you can use anything you like.
But if your speakers are muddy and weak, so will be your sound. Using your home
stereo will generally give good high-frequency range, but if you go this route be
careful. The Prophet has much more dynamic range than the typical stereo source. It
can generate powerful transients which can damage component speakers if the volume
is set too high. Therefore, you might consider using amplifiers and speakers specifical-
ly designed for electronic instruments.
To protect speakers, it is customary to switch off amplifier power when connecting
cable from the Prophet's AUDIO OUT jack.
Connection and use of the enclosed footswitch is explained in paragraph 1-5. For other
back-panel connections, see Section 3.
1-2 POWER-ON AND INITIAL TUNING
The Prophet is turned on with the POWER switch on the back panel. After the
instrument is switched on, the front panel will be dark—except for the TUNE switch—
for approximately eight seconds while the computer tunes the oscillators. When tuning
is completed the front panel will light up and the BANK-PROGRAM numeric display in
the PROGRAMMER section of the front panel will display "1-1". This indicates that
the Prophet is ready to play and that its voices are programmed according to the
settings stored in BANK 1PROGRAM 1of the computer's memory.
To adjust the overall volume and tuning, hold down asingle key on the keyboard (e.g.
middle A) and adjust the VOLUME and MASTER TUNE controls on the right side of the
front panel.
1-2 CMIOOOD 2/82

The Prophet has abuilt-in, crystal-referenced A-^f^O Hz oscillator which is accurate to
1Hz in any environment. This reference oscillator is enabled by hitting the A-4<^0
switch. The LED indicator in the switch will light. To turn the A-'t^O tone off, hit the
switch again.
1-3 PRESET SELECTION
Since the Prophet is shipped with afull complement of 120 factory programs it will be
ready to play as soon as initial tuning is completed. At this point the Prophet
automatically enters PRESET Mode, meaning that it is ready to patch the synthesizer
voices according to aprogram stored in the Prophet's microcomputer memory.
The 120 programs are organized as three 'tO-program files. Only one file can be active
in the PROGRAMMER at atime. Each *0-program file is in turn arranged as five
banks of eight programs each. The BANK SELECT switch steps through the file's five
banks in order, and the eight PROGRAM SELECT switches (numbered 1through 8)
allow immediate selection of aparticular program within abank.
When the Prophet first "comes-up," Program File 1is active. To choose one of these
40 programs, step through the banks until you reach the desired BANK then press the
PROGRAM SELECT switch for the program you wish. The selected bank will be
indicated by the numeric display, and the selected program will be indicated both by
the numeric display and by an LED embedded in the PROGRAM SELECT switches.
To select Program Files 2 or 3, hold the BANK switch and press PROGRAM SELECT 2
or 3. This will bring afresh set of 40 programs to the PROGRAMMER. The file number
is indicated on the numeric display with decimal points: no decimal point indicates File
1; adecimal point after the BANK digit indicates File 2; adecimal point after the
PROGRAM digit indicates File 3. (To return to File 1, hold BANK and press
PROGRAM SELECT 1.)
All factory programs in the three files are charted in Section 8. Also included are
specific patch diagrams and comments for Program File 1. The three program files are
also recorded on the included cassette. Use of the cassette interface for program
storage is discussed in Section 4.
The Prophet can also be operated in MANUAL Mode (PRESET off), with the knobs and
switches functioning as described in Section 2.
1-* PITCH AND MOD WHEELS
The PITCH and modulation (MOD) wheels are located to the left of the keyboard. Both
wheels affect all voices simultaneously. The PITCH wheel has a center detent position,
from which the pitch of all voices may be varied up or down by about a5th.
The MOD wheel determines the amount of modulation routed via the WHEEL-MOD
settings of aparticular program. When the wheel is fully down no modulation will
occur, and when the wheel is fully up amaximum of modulation will occur. For
information on the effects that may be engaged within Program File 1, see the notes
accompanying each patch diagram in Section 8.
CMIOOOD 2/82 1-3

1-5 RELEASE FCXJTSWITCH
In PRESET Mode, if the RELEASE switch is programmed to be off, but the program
also contains an amplifier envelope release setting which can have an audible effect,
this release can be engaged either by switching RELEASE on, or by using the included
footswitch (which connects to the RELEASE FOOTSWITCH jack on the back panel).
The footswitch will function like the RELEASE switch on the front panel, except it
only operates when the RELEASE switch is (programmed) off. The footswitch then
takes the place of the RELEASE switch. When pushed, the programmed amplifier
release cycle is enabled. When not pushed, the amplifier release cycle is set to
minimum. In this respect, the footswitch functions similarly to apiano's sustain pedal.
Further expressive influences on the Prophet's programs can be brought about through
the use of other accessories which connect to the Prophet's back paneL For
information on these possibilities, see Section 3.
1-6 RETUNING
Although the microcomputer tunes the oscillators when the Prophet is first turned on,
it will occasionally be necessary to retune, particularly during the first few minutes of
operation since the oscillators need time to stabilize. (After 20 minutes or so the
instrument should not have to be retuned very often, unless there is aradical
temperature change in the room.)
Hitting the TUNE switch will tell the computer to retune the oscillators. During this
process the control panel goes dark—except for the TUNE switch—for two to eight
seconds (depending on how far out of tune the oscillators were), then will return to the
previous front panel status.
1-7 VOICE ASSIGNMENT
The microcomputer assigns the five synthesizer voices to keys played on the keyboard.
If the same key is struck repeatedly, the microcomputer assigns the same voice. If
more than five keys are held down at the same time, the computer will reassign the
earliest used voices first. For example: playing C, D, E, F, G, and Ain succession and
holding all six keys down will cause D, E, F, G, and Ato be sustained—the Cwill
disappear when the Ais played. In other words, the Prophet normally operates on a
"last-note priority" system: each new note played is assigned to the earliest-used
voice.
There is an exception to this system. If the UNISON switch is on, all five voices are
assigned to asingle key. In keeping with conventions established by monophonic
synthesizers, UNISON assigns priority to the lowest key held.
1-8 VOICE DEFEAT
For the occasion when avoice may become unplayable due to component failure, a
Voice Defeat allows you to delete the failed voice from the assignment system. The
Prophet can then be played normally, with the remaining voices.
l-^^ '• CMIOOOD 2/82

To defeat avoice, hold the key it is currently assigned to with one hand while holding
PROGRAM SELECT 1and pressing PROGRAM SELECT 8. The voice will be defeated
and will remain defeated until the Prophet's power is switched off. (When power is
switched back on, the voice will not be defeated.)
1-9 EDITING AND RECORDING PROGRAMS
NOTE; The following directions are to simply get you started. More information on
editing and recording programs is in paragraph 2-1.
While any program is selected, you can experiment with changes to it by toggling the
switches and adjusting the knobs. This is "editing." Once you move aknob, it becomes
"active," showing its actual setting on the panel. (Unmoved knobs do not necessarily
show their actual setting in the current program.) The original program remains
unchanged, and can always be recalled by just hitting its PROGRAM SELECT switch.
In general, to record an edited program, the RECORD switch is pressed on, then the
desired destination BANK and PROGRAM location are selected.
NOTE; To protect the program memory from accidental erasure, RECORD Mode can
only be entered if the back panel RECORD ENABLE/DISABLE switch is up (ENABLE).
The switch should probably be left in the DISABLE position until the modes of
operation and control functions are well understood. This will ensure against acciden-
tal erasure of the original factory programs. However,remember that accidental
erasure is not adisaster, since the factory programs can be re-programmed into the
Prophet at any time through the cassette interface, as explained in Section ^.
The exact program-RECORD procedure is as follows;
1. Check that the back panel RECORD ENABLE/DISABLE switch is set to the
ENABLE (up) position.
2. Switch on the orange RECORD switch in the PROGRAMMER section. It will light.
3. Select the desired destination program file (1, 2, or 3), using the BANK and
PROGRAM SELECT switches. (Ignore this step if the current file is desired.)
i^. Select the desired bank using the BANK SELECT. (Ignore this step if current BANK
is desired.)
5. At this point you can exit RECORD Mode by switching the RECORD switch off.
The memory will not be affected.
6. Otherwise, press any PROGRAM SELECT and the program will be recorded at the
corresponding number in the selected bank. NOTE; Be sure to hit the correct
PROGRAM SELECT switch or you may erase aprogram you wanted to keep.
7. When aPROGRAM SELECT switch has been hit, the RECORD LED will go off and
the Prophet will return to the mode it was in before recording.
8. After recording aprogram, it is always agood idea to check that the program is
correctly recorded in the desired location by pressing the PROGRAM SELECT again.
CMIOOOD 2/82
'
1-5

SECTION 2
FRONT PANEL
2-0 INTRODUCTION
This section explains the modes of operation and functions of the controls comprising
the "modules" (for example, OSCILLATOR, FILTER, AMPLIFIER, and LFO) outlined
on the front panel. The alternatives of each switch and ranges of each knob are
described relative to the overall signal flow of the voices and to the modulation
circuitry.
Section 1introduced basic PRESET operation with the factory programs accessible
through the PROGRAMMER. It is true that the Prophet can be used exclusively in
PRESET Mode, in which case the voice and modulation controls would not be used very
often. However, using the instrument solely in this way defeats alarge part of its
overall purpose, which is to allow keyboard synthesists to create and record sounds
appropriate to their own music. The creation of satisfying custom programs depends
entirely on familiarity with the controls described below.
By the way, in describing the front panel, this section will not attempt to comprehen-
sively explain synthesis technique. However, by referring to the patch diagrams in
Section 8while playing through the factory programs, you will soon grasp some of the
sonic possibilities the Prophet makes available. To gain familiarity with the voice and
modulation controls, we encourage you to edit the factory programs. Programs 5-7
and 5-8 (in File 1) are specifically included for editing practice—please see the notes
accompanying these programs in Section 8.
For more information on synthesis technique, refer to the books and magazines listed
in Section 7.
2-1 MODES OF OPERATION
The Edit feature of PRESET Mode is apowerful tool that allows you to experiment
with program changes by selectively adjusting the front panel controls. The original
program remains unchanged and can be restored at any time by simply hitting its
PROGRAM SELECT again.
In addition to PRESET, the Prophet has MANUAL and RECORD Modes of operation.
In MANUAL Mode apatch can be formed entirely "from scratch." RECORD is a
momentary mode for storing or relocating programs. A"patch" becomes a"program"
when recorded. Custom programs can therefore be created in two ways: 1) by
recording manually-formed patches or 2) recording edited programs. Edited programs
can be recorded into the original location if the original program is not desired, or in a
new location.
The front panel controls are color-coded to clarify the modes of operation and the
function of the computer's memory. All black knobs and switches are programmable:
that is, their settings can be recorded into memory and recalled in PRESET Mode.
CMIOOOD 2/82 2-1

The silver knobs (MASTER TUNE and VOLUME) and grey switches (PROGRAMMER,
TUNE, A-440, SAVE TO TAPE and LOAD FROM TAPE) are not programmable. The
PITCH and MOD wheels are also not programmable. (The RECORD switch is orange so
it can easily be distinguished.)
All of the switches except BANK SELECT have LED indicators embedded in them.
And, except for the eight PROGRAM SELECTS, SAVE TO TAPE, LOAD FROM TAPE
and TUNE, all LED switches are alternate action: one push turns them on, the next
push turns them off. For example, the PRESET switch LED when lit indicates PRESET
Mode. When the Prophet is switched to MANUAL Mode by pushing the (lit) PRESET
switch, the LED goes off.
In MANUAL Mode the control panel always indicates the status of the patch under
construction. You can see exactly what signal paths are closed by (lit) switches. The
knob settings reflect their actual values. Note that in PRESET Mode as you select
different programs, the switch LEDs indicate how the switches are programmed. But
there is no way for the knobs to move themselves—they just stay where they were last
set. So, in PRESET Mode the knobs do not normally indicate their "current" setting.
However as soon as you move aknob to EDIT aprogram, that knob converts to
MANUAL operation. So only the knobs you move will actually indicate their current
setting: the parameters controlled by unmoved knobs do not change.
For example, suppose you like program 3-3 but want to change OSC Apitch and prefer
abrighter tone. In PRESET Mode, select BANK 3-PROGRAM 3, adjust OSC A
FREQUENCY to the desired pitch and increase the FILTER CUTOFF to the desired
brightness. You can cancel any changes and return to the original program by hitting
PROGRAM SELECT 3. If you want to permanently program location 3-3 to your edited
version, record it in 3-3. Or, if both the original and the edited version are wanted,
record the edited program in anew location (that is, alocation with an undesired
program).
For afurther discussion of recording and relocating programs, see the notes following
programs 5-7 and 5-8, in Section 8.
2-2 VOICE SIGNAL FLOW
The Prophet's audio output results from several stages of signal generation, combina-
tion, and modification. The front panel is divided into VOICE and MODULATION
sections. MODULATION controls are covered in paragraph 2-9. It should be kept in
mind that while only one voice is depicted on the panel, the voice controls patch five
voices in parallel. Figure 2-0 diagrams signal flow in asingle voice. Basically, the
MIXER sets OSCILLATOR (VCO) A, B, and NOISE levels sent to the FILTER (VCF) and
AMPLIFIER (VCA) where, roughly speaking, the timbre and dynamics are shaped.
Finally the voices are combined and the overall level set by the VOLUME control.
Each voice module is detailed in paragraphs 2-3 through 2-7.
2-2 CMIOOOD 2/82

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CMIOOOD 2/82

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2-3 OSCILLATOR A
CSC Ais an audio-frequency source always under control of the keyboard.
OSCILLATOR A
/I n
*• II*
10
rREOUfMCV
10
PULSE WIDTH
Figure 2-1
FREQUENCY knob; Controls pitch (oscillator tuning). Stepped (quantized) in semitones
over afour-octave range. Exact pitch is set with the MASTER TUNE knob.
SAWTOOTH SHAPE switch; When on, enables afull-level sawtooth wave containing all
harmonics. This unmodified shape is often described as "brassy."
PULSE SHAPE switch; When on, enables afull-level rectangular wave whose harmonic
content depends on the setting of the PULSE WIDTH knob.
If neither SHAPE switch is on, OSC Awill have no output to the mixer. If both SHAPE
switches are on, the sawtooth and pulse are mixed at full level and supplied as OSC A's
output to the mixer.
PULSE WIDTH knob; Adjusts the harmonic content of the pulse wave by setting its
duty cycle from approximately 1to 99%. A50% duty-cycle pulse (having only odd
harmonics), also called asquare wave, can be obtained by setting the knob to
approximately 5, then carefully adjusting for the dropout of the second harmonic (the
first octave overtone). Of course this knob is only effective if the PULSE SHAPE
switch is on.
At the extreme knob settings the pulses may "thin out" until they degenerate to dc,
resulting in no output signal.
This knob has no effect on the sawtooth wave.
SYNC switch; Forces OSC Ato follow OSC Bin "hard" synchronization, so it will
therefore tune only to harmonic frequencies of OSC B. Intermediate FREQUENCY
knob settings will produce unusual wave shapes (and therefore unusual timbres) at the
next lower harmonic of OSC B.
When awide-width pulse is selected for OSC Ain sync with OSC B, and OSC B's
frequency is set much higher than OSC /K, the signal from OSC Amay degenerate to
dc since the pulse is not given achance to discharge before being resynced.
To gain an understanding of SYNC effects, check programs l-'t, 1-7, 2-7, 3-2, '^-2, and
^-5 in Program File 1.
2_i^ CMIOOOD 2/82

2-4 OSCILLATOR B
CSC Bis similar to OSC A, except that in addition to being akeyboard-controlled
audio-frequency source it can also be alow-frequency modulation source with or
without keyboard control. The identically-named controls function as described under
OSC A. In addition:
OSCILLATOR B
'^' •^' WW % •'^'-
10 O10 IHaPE "> LOFREQ KEYBOMW
FREauEMCY FINE PULSE WIDTH
Figure 2-2
FINE knob; Continuously varies pitch over asemitone range, up from the basic pitch
setting of the FREQUENCY knob. This is useful for detuning OSC Brelative to OSC A.
When no detuning is desired, the FINE knob should be set to 0.
TRIANGLE switch; Enables full-level triangle wave, containing little harmonic energy.
So as to not offset modulation destinations, this output is centered about ground.
NOTE; When no waveshapes are switched on, OSC Bprovides no output. However, if
OSC ASYNC is on, the overall pitch range of the program may still be determined by
the OSC BFREQUENCY knob setting.
LO FREQ switch; Converts OSC B's function to alow-frequency oscillator (LFO), with
arange of approximately 0.^ Hz (or, 1cycle every 2.5 seconds) to 30 Hz. This function
is usually used in conjuntion with the POLY-MOD section (see paragraph 2-9).
KEYBOARD switch; When on, OSC Bfrequency is controlled by the keyboard. When
off, OSC Bfrequency will be independent of the keyboard.
When OSC Bis used as an audio source, usually LO FREQ is switched off and
KEYBOARD is switched on. (For some exceptions to this rule, check some of the
programs in bank 5of Program File 1.)
If the LO FREQ and KEYBOARD switches are off, OSC Bwill act as adrone in the
audio range. Set the pitch of this drone with the OSC BFREQUENCY knob after the
KEYBOARD switch is switched off. Otherwise you may have to retune.
CMIOOOD 2/82 2-5

2-5 MIXER
MIXER
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OSC Aand OSC Bknobs; Adjust the level of oscillator input to the filter.
NOISE knob; Adjusts the white noise level input to the filter. Noise is an unpitched
combination of all frequencies useful for such sounds as drums, cymbals, surf, or rain.
These MIXER knobs are also used to set overall volume of the patch so when switching
between PRESET programs, one program won't be wildly different in volume from
another.
2-6 FILTER
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Figure 2-4
The FILTER module contains controls for the filter itself and for its envelope
generator.
CUTOFF knob; This adjusts cutoff frequency of the 24 dB/octave Cf-pole) low-pass
filter. It is rather like atone control. "Cutoff" is the frequency below which all
elements of the mixer's output signal are let through. The higher-frequency compo-
nents of the input signal (i.e. all those above the cutoff frequency) are suppressed. The
higher the knob setting, the higher the frequencies are which pass through the filter.
Thus, the "brighter" the sound.
2-6 CMIOOOD 2/82

RESONANCE knob; Adjusts the amount of filter resonance. As the setting is increased
from to approximately 7the amount of resonance ("emphasis," "regneration," or "Q")
applied to those signal components at the cutoff frequency will increase. As resonance
increases, frequencies lower than the cutoff will become decreasingly audible in
comparison with those nearer the cutoff. As the knob setting is increased beyond 7,
the filter breaks into oscillation, acting like asine-wave audio source whose pitch is
determined by the cutoff frequency.
ENVELOPE AMOUNT knob; The filter cutoff may be contoured (shaped) electronically
according to avoltage pattern provided by the envelope generator. The specific
envelope is shaped by the ATTACK, DECAY, SUSTAIN, and RELEASE (ADSR) knobs.
The ENVELOPE AMOUNT knob is an attenuator which sets the depth of the applied
envelope. Creating the envelope itself with the ADSR knobs is discussed below.
KEYBOARD switch; When on, the KEYBOARD control voltage (CV) is applied to the
filter's cutoff frequency just as it is normally applied to OSC Aand optionally applied
to OSC B. With the filter thus "tracking" the keyboard, its cuttoff frequency is
maintained at aconstant point relative to the notes being played. This results in a
consistency of timbre over the whole keyboard range. When FILTER KEYBOARD is
switched off, notes played higher on the keyboard will have more of their overtones
suppressed than notes played lower. As aresult, the higher notes will have aduller
timbre.
If FILTER RESONANCE is set for self-oscillation (e. g. above 7), then switching
FILTER KEYBOARD on will allow the filter to be played from the keyboard. Unless a
complex effect is desired, the FILTER ENVELOPE AMOUNT knob will in this case
normally be set to (to maintain asteady response from voice to voice).
LEVEL
ENVELOPE
AMOUNT
(fTlLTER ONLY)
TIME
LENGTH OF TIME THAT KEY IS HELD DOWN
Figure 2-5
ENVELOPE
The filter envelope generator contours timbre by controlling the filter cutoff
frequency. The contour pattern is initiated when akey is struck, producing agate. The
initial appearance of the gate "triggers" the envelope generator(s) to proceed through
their attack and decay periods. After the attack and decay periods set for each
envelope generator have elapsed, the generator will produce asteady control voltage
(CV) at the level set by the SUSTAIN knob for as long as the GATE is present
(indicating the key is held). When the key is released, the GATE goes off and the
envelope generator output voltage drops to zero at arate set by the RELEASE knob.
CMIOOOD 2/82 2-7

ATTACK knob; Adjusts the length of time for the envelope generator's output to go
from zero level (when key is initially depressed) to maximum level.
DECAY knob: Adjusts the length of time for the envelope generator's output to go
from maximum level to sustain level.
SUSTAIN knob: Adjusts the sustain level from zero to maximum. Remember, this is a
level control, not atime control. (Sustain time is the period between the end of the
DECAY period and the beginning of the RELEASE period. This is determined by
touch.)
If SUSTAIN is set at maximum then the DECAY knob setting is irrelevant, because
there is no level below maximum for the envelope to decay to.
RELEASE knob; Adjusts the length of time for the envelope generator's output to go
from sustain level to zero.
If the key is released before the attack or decay periods have elapsed, the RELEASE
knob controls the time taken for the output to drop to zero from whatever its level
when the key was released.
If the attack and decay periods have elapsed and SUSTAIN is set to 0, then the
RELEASE setting is irrelevant, because there is no level for the envelope to release
from.
NOTE: The time range on the ATTACK, DECAY, and RELEASE knobs is approximate-
ly 1millisecond (1/1000 second) to 30 seconds. Since the generators respond exponen-
tially to their timing CV inputs, setting 5, for example, gives aperiod of approximate-
ly 1/2 second (rather than 15 seconds).
Remember that the FILTER ENVELOPE AMOUNT knob governs the depth of filter
contour. So if ENVELOPE AMOUNT is set to 0, the envelope generator will have no
effect on the filter.
2-7 AMPLIFER
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Figure 2-6
The ATTACK, DECAY, SUSTAIN, and RELEASE knobs in this module shape the
envelope applied to the VCA in the same manner as the corresponding controls in the
FILTER module.
Unless the SUSTAIN knob is somewhat advanced, nothing will be heard after the
ATTACK and DECAY periods have elapsed.
2-8 CMIOOOD 2/82

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2-8 MISCELLANEOUS
RELEASE switch; This was discussed in paragraph 1-5. When switched off, the filter
and amplifier release times are programmed to aminimal setting so there will be no
release but also no audible "whack" which would be caused by the instantaneous closing
of the VGA. To allow operation of the release footswitch, the RELEASE switch must
be off.
UNISON switch; When this switch is on, the Prophet-5 will assign all five voices to the
lowest note played. The Prophet thus becomes avery "fat" monophonic synth. When
the monophonic sequencer interface (see paragraph :3-3) is being used, four voices will
be available for UNISON assignment.
GLIDE knob; Effective only when UNISON is on, the GLIDE module is a"lag processor"
which can delay the rate at which the KEYBOARD CV (which controls the oscillators
and filter) can change. When set to the KEYBOARD CV instantly steps between
notes. As the GLIDE knob is advanced, the CV does not step between the notes, but
begins to "slew." This introduces "portamento" between notes.
2-9 MODULATION
Asynthesizer's expressiveness stands oh its modulation facilities. The term "modula-
tion" refers to aperiodic or consistent (as opposed to random) aural change which is
interesting or musically useful. Modulation is created by electronic controllers when it
is not possible to adjust amechanical controller with the required speed or precision.
Modulating devices therefore free the hands for playing the keyboard.
Modulation involves the signal-generating source and the modulated destination.The
Prophet contains two distinct modulation systems: WHEEL-MOD and POLYphonic-
MOD. The WHEEL-MOD system (see Figure 2-7) has two sources, LFO and pink noise,
and five destinations; OSC Afrequency and pulse-width, OSC Bfrequency and pulse-
width, and filter frequency.
In the LFO module, the FREQUENCY knob adjusts LFO frequency from approximatley
0.0^ Hz (or, 1cycle every 25 seconds) to 20 Hz. The SHAPE switches select the full-
level modulating waveforms. In the WHEEL-MOD module, the SOURCE MIX knob
determines the relative amount of LFO or noise sent to the destination; for all LFO
as source and 10 for all noise as source. To the left of the keyboard, the MOD wheel
itself determines the actual modulation level.
In addition to the WHEEL-MOD system, the Prophet's unique POLY-MOD system (see
Figure 2-8) provides routings within each voice for two sources, the filter envelope
generator or OSC B, to modulate three destinations: OSC Afrequency, pulse width, or
filter frequency. Although the routings are exactly the same for each voice, the
minute but omnipresent differences between the voices (e. g. phase relationship of the
oscillators) will create modulation effects that will be unique from voice to voice or
note to note. This is in direct contrast to the effect of WHEEL-MOD, where one signal
is applied equally to the voices, yielding the same effect from note to note. (There will
be no POLY-MOD if the two SOURCE AMOUNT knobs are set to or if the three
destination switches are off.)
CMIOOOD 2/82 2-9