Conn STROBOCONN User manual
PIANO
TUNERS
MANUAL
HOW
TO
USE
THE
IN
PIANO TUNING
CONN
Conn
Corporation
•
Elkhart,
Indiana
PIANO
TUNERS
MANUAL
HOW
TO
USE
THE
IN PIANO TUNING
CONN
Conn
Corporation
•
EI
kha rt,
India
na
Copyright,
1956,
by
c.
G.
Conn Ltd.
Revised
1963
STROBOCONN "PIANO TUNING" MANUAL
How
to Use
the
STROBOCONN
Piano Tuning
TABLE OF CONTENTS
•
In
Page
INTRODUCTION
_ _ _
__
..
_._.
._
_.
__
_
__
_ 3
SETTING
UP
THE
STROBOCONN. . . _
..
__
.
__
..
3
HOW
TO
START
THE
STROBOCONN
..
-
_.
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..
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_
..
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..
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__
. 5
READING
THE
STROBOCONN
__
..
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..
_
__
..
__
__
. 5
1.
Scanning
Unit
.
__
_.
__ __
..
_
..
_
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__
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__
. 5
2.
Tuning
Unit.
__
. .
__
......•..
..
_.
.
._.
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_
__
.
._
_.
6
3. Transposition Indicator
..
_ _
__
_ _
__
.'
__
"'"
_ _ _
__
-
-.---
8
TUNING
THE
PIANO
__
_
__
..
_
__
_ _ _ _
__
._
_
..
_
__
-.--
9
1. Placing the Stroboconn
in
Position
__
_
..
__
.
__
_ -
._.
9
2.
Locating the Microphone
_.
__
. . _
..
.
__
..
.
__
_ 9
3.
Tuning
Procedure
..
_
..
_
..
__ __
_9-10-11
MISCELLANy
__
..
_._
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_
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._._
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_
..
_
12
1.
Lower Octave Patterns
..
._
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._
_._
_ _
..
_
..
__
.
__
__
.. ..
__
.
__
.
__
_.
__
..
12
2.
"Stretched Octave"
Tuning
.
._
..
__ __
._
..
.
._
..
_ _
..
__
.
12
3.
Setting the Temperament.
__
. . _
__
_._
..
_.
__
.
__
._.
. _
..
_ _ .12
4. Microphones, Airborne and Contact
__
_._
..
_
..
_
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._
_ _ _
..
__
..12
5.
Low-Pass Filter .
._
_ _
..
_
..
_
_.
.
._
__ __ __
.
__
..
_ _
12
PAGE
TWO
STROBOCONN
"PIANO TUNING" MANUAL
INTRODUCTION
The
Stroboconn is
an
electronic device
for
instanta-
neous
and
accurate visual measurement
(or
comparison)
of
sound frequencies. Its frequency range is from 31,772
to 4,066.8 cycles
per
second-essentially
covering the
range
of
the piano keyboard.
The
Stroboconn is
now
widely
known
and is rapidly
becoming adaily byword among piano tuners
and
tech-
nicians
throughout
the world.
It
is ahighly scientific
addition to the traditional
"tools
of
the trade," which
enables
the
tuner
to
carryon
his skilled
work
more
rapidly
and
with
more
confidence
than
ever before.
Here
are some
of
the most practical
and
helpful
ways
in which the
STROBOCONN
saves
time
and
increases
the
earni11gs
of
the tuner!
1.
Time
consuming
and
difficult "setting
of
tempera-
ment"
is speeded
up
to
require
no
more time than
other
octaves. Each note is tuned visual1y, quickly,
and
the temperament is automatically set.
2.
Time
required
to
"beat"
(count
beats) is elimin-
ated-visual
pattern
appears immediately.
3.
Time
required for total
tuning
job may be greatly
reduced with this advanced method.
4. Apermanent, visual record
of
each
tuning
can be
kept
which enables
an
exact duplication
of
the
tuning
job
at
any time.
5.
Piano can be tuned to standard
of
A-440-or
any
other
standard
of
frequency,
with
equal ease.
6.
Piano can be tuned
with
ease to mean-tone scale,
Pythagorean Scale,
Just
Scale,
or
any
odler
scale.
7.
The
amount
of
octave stretching required by each
piano can be measured
with
the Stroboconn, en-
abling the technician
to
achieve the best sound
the piano is capable
of
producing.
8.
Enables the technician to use more
of
his percep-
tion powers by using
both
eyes and ears
to
give
less chance
for
error
and means for quick checks
to see
if
any accidental change has ,occurred.
9. Many tuners are getting
higher
prices
for
Strobo-
conn tunings.
10.
Although
this is asimplification and extension
of
atechnique already used by some technicians, it
provides,
for
the first time,
an
accurate and de-
pendable visual guide.
11,
Proof
of
the accuracy
of
the
tuning
job
can be
given
the
customer by showing him the visual
reading
on
the Stroboconn.
This
creates customer
confidence and satisfaction.
12.
Makes possible "identical" tunings for two
or
more pianos to be used together
or
for
piano and
organ.
13.
Makes accurate
tuning
possible in noisy sur-
tOundings.
The
information which follows will
help
darify
many
questions which may occur to you in connection with the
use
of
the Stroboconn in piano tuning!
In
addition,
it
is also urgently suggested
that
the operator's manual be
studied carefully before using the instrument.
..-
Figure
I-Pictured
above
is
Model
6T-3
Stroboconn,
complete
with
desk·type
microphone,
one
encased
Scanning
Unit,
one
encased
Tuning Unit,
and
necessary
interconnecting
electrical
and
a-c
power
cables.
SEnlNG
UP
THE
STROBOCONN
Set
up
the two cases comprising the Stroboconn
on
wise
to
lock them
in
place.
(It
is impossible
to
insert the
their wide sides with handles to the right, unlatch covers connectors improperly.) Assemble microphone stand
afnd
remove cables, microphAone, and
m~crophdone
stand insert microphone
plug
into its
input
receptacle on
th~
rom cover compartment. rrange .
umts
an connect
..
.
cables as shown in Figure
2.
The
two-prong
plug
goes
to
scannmg umt, and
turn
the volume control to the rIght
the power receptacle, and the three-prong cable connects
to
~AXIMUM.
(To
save space, and gain
height
for
the two units.
After
inserting the three-prong 'plugs
on
eaSler reading,
it
is suggested
that
the Scanning
Unit
the interconnection cable, give each afirm
tWlSt
clock- be placed on
top
of
the
Tuning
Unit-Figure
2.)
PAGE
THREE
II
12-
13
14-
STROBOCONN "PIANO TUNING" MANUAL
2
3
l-.----9
----10
1.
Microphone
2.
Scanning
Unit
3.
Transposing
Knob
4.
Motor
Switch
Figure
2-The
Complele
SIroboconn,
Model
6T-3
5.
Power
Switch 9. AC Connector
6.
AC
Power
Cable
10.
Tuning
Unit
7.
Interconnection Cable
11.
Scanning
Windows
8.
Tuning
Unit
Scale
(Sharp
12.
Key Signature
Window
Side)
13.
Volume
Control
PAGE
FOUR
14.
Microphone
Connection
15.
Tuning
Unit
Scale
Pointer
16.
Tuniog
Scale
(Flat
Side)
17.
Tuning
Knob
STROBOCONN "PIANO TUNING" MANUAL
CAUTION:
The
Stroboconn is designed to operate
on
apower source supplying 105-120 volts, 50-60 cycle
alternating current. Connection
to
improper
power
source may cause damage
to
the instrument.
If
operation
on
direct current is required, aconverter must be used.
FOR
OPERATION
ON
LOW
LINE
VOLTAGE:
The
6T-3 Stroboconn is equipped with aline voltage
switch to provide normal
motor
drive power
under
conditions
of
low
power line voltage.
The
NORMAL
position is recommended
for
all occasions
of
use except
when the power line voltage is
so
low
that
the scanning
unit
motor
will
not
drive the discs synchronously. This
condition will be evidenced by the blinking
of
the
motor
pilot
light
or
by oscillation
of
the observed
stroboscopic pattern.
CAUTION:
Operating
the Strobo-
conn with the switch
in
the
LOW
line voltage position
on
normal line voltage, however, will subject
the
tubes
and
electrical components
to
undue strain, possibly
shortening their lives
and
causing failure
of
the instru-
ment.
HOW
TO START
THE
STROBOCONN
To
turn
on, first
lift
the
No.1
or
"Power"
switch
at
the extreme
right
hand
end
of
the scanning
unit
to
the
ON
position.
No.
2switch should be pushed down
to the
WARM-UP
position,
and
about forty seconds
allowed
for
the vacuum tubes to warm up.
(This
allows
the fork
to
build
up
its vibration sufficiently
to
drive the
motor,
and
will be shown by the
MOTOR
PILOT
light
in
the center
of
the scanning
unit
glowing stea.dily.)
The
No.2
switch
at
the
right
side
of
the scanning
unit
should
now
be lifted to the
RUN
position.
This
trans-
fers the power from the
motor
to the
fork
drive
and
turns
on
the Microphone Amplifier, which takes about
twenty seconds
to
heat
up. Sound reaching the micro-
phone should then cause the windows in the mask to be
illuminated.
If
the
MOTOR
PILOT
light
does
not
glow
steadily,
but
blinks after the
No.2
switch has been lifted,
the fork has
not
been allowed sufficient time to build
up
its vibration,
and
the
No.2
switch should be pressed
down and alittle more time allowed.
When
the above operations have been performed the
Stroboconn is ready
for
use.
(Refer
to
Fig. 2
for
identification
of
Parts
mentioned.)
READING
THE
STROBOCONN
With
the Stroboconn the frequency
of
any tone lying
within the essential range
of
the piano keyboard may be
determined directly.
The
method is entirely visual
and
does
not
involve the sounding
of
any comparison tone.
Deviations are measured from the tones
of
the equally
tempered scale based
on
the standard A
of
440 cycles
per second.
While
a
high
order
of
accuracy is attained, the process
of
measurement is simple
and
rapid
and
the readings
are obtained directly
without
further
computation
or
reduction.
The
appearance
of
the Stroboconn,
as
set
up
for
use,
is illustrated
in
Figure 1. Figure 2also shows the two
units, with parts identified, the one above being labeled
"Scanning
Unit,"
and the lower being labeled
"Tuning
Unit."
In
the Scanning Unit, as is seen in Figure
2,
there
are twelve windows having the relative positions
of
the
white
and
black keys
of
the piano keyboard,
in
the octave
from C
to
B.
The
twelve notes
of
the chromatic octaves
are thus represented, the
top
row
of
windows corres-
ponding
to
the black keys,
and
the bottom
row
corres-
ponding
to
the white keys. Sound picked
up
by the
microphone causes these windows to be illuminated.
Each window is
in
front
of
a
round
disc having cer-
tain printed
patterns-Figure
3. These discs revolve at
different speeds, being driven by gears
at
different ratios,
and
appear
to
have seven bands
in
the
printed
pattern.
Aneon tube circles the disc inside the unit,
and
when
asound is picked
up
on
the microphone
it
causes the
tube to
light
up
or
flash according to the number
of
PAGE
sound wave vibrations.
When
these flashes correspond
to the same
number
of
black squares
turning
past the
window
on
adisc, the lighted
pattern
appears to stand
still. This is the same stroboscopic principle with which
you are familiar
in
the movies, where the spokes
of
a
wagon wheel may appear to stand still,
or
go backwards.
If
the
pattern
is
turning
slightly faster
than
the
light
flashes, each spoke
or
square will appear
to
be slightly
ahead
of
the last one, giving the optical illusion
of
a
moving
pattern
turning
clockwise. (Fig.
8)
For
example, supposing
that
the scale
pointer
is set at
..
zero,
and
that
apiano
"A"
string
is sounded tuned
to
440 vibrations
per
second.
There
will appear across the
center
of
the
"A"
window acharacteristic stationary
pattern composed
of
alternate
light
and
dark bars, having
an
appearance similar to
that
shown
in
Figure 4.
Upon
sounding the A
an
octave
higher
(A-880), a
similar
pattern
appears
in
the same window
with
twice
the
number
of
bars, since the frequency is doubled. (Fig.
5)
The
position
of
the pattern, however, is shifted out-
ward
from the center to the next
band
in
the window
pattern
(compare
Fig
4
and
5).
Bands are provided
for
seven octaves
so
that
anyone
of
the seven A's within
the piano range can produce its own appropriate sta-
tionary
pattern
on
its appropriate octave band.
(Fig
6)
Sounding the seven A#'s will similarly cause patterns
to
appear
in
the
A#
window,
and
sounding the seven B's
will cause patterns
to
appear
on
the seven bands
of
the Bwindow, etc. Since there are twelve windows, there
FIVE
STROBOCONN "PIANO TUNING" MANUAL
is
space
provi~eldl
for 7 x
~2,
or
h
84
"'l,~~\~'l\~II'
~rlrl
TdehPar.tsf
from. standabrd
btu
n.i
ng
d
·
notes, essentla y
covenng
t e
..
~"
.\
'I
I,
Ij
Ij
IS
10
ormation
can e0tatne
range
of
the piano keyboard. (See
~w~
~r~~
by
simply
turning
the scale point-
Fig.
6).
(Procedure for tuning
~m~"
~'~~~"""~
er until the
pattern
stops.
Aa,
Alia,
Ba
and
Cs
will be ex-
~~"'
~~
Take,
for
example, an Awhich
plained later.) has been tuned flatter
than
stand-
The
foregoing explanation
as-
_~
•
~
ard, say
to
435 vibrations
per
sumes
that
the
pointer
on
the tun- _
-==
second instead
of
440.
In
the
"A"
ing
unit
has been left at zero.
::-.
~
window the
pattern
will be seen
With
the scale
pointer
set at zero,
::::.-.
..
_apparently moving toward the
the Stroboconn is in exact tune _
~
....,::::: left. (Fig.
8.)
Now
by moving
with the equally tempered scale
~%~
~~
the scale
pointer
in
the same dir-
based
on
A-440 vibrations
per
~
...
~
~
...
~
ection, to the left, the
pattern
may
second.
With
the pointer set to
';tI'.4~
~
~
be
brought
to astandstill.
any position other than zero all
~h~
tJ
~
~
The
pointer
will then read
notes are equally changed in hun-
~);!,
,fJ
1'~~\
~,~
"-20"
on
the graduated scale
dredth
parts
of
semitone; and
IIIi
\~",
above the adjusting knob, thus
the Stroboconn is still in
tune
showing directly
how
much the
with
the
equally
tempered
scale Figure
3-Stroboconn
Scanning
Disc
in Stationary 435-vibration tone
is
flat com-
based,
in
this case,
on
an A
of
Position. pared to the standard A
of
440-
some
other
frequency.
(Figure
7the reading being expressed in
shows
the
vibration frequencies corresponding
to
hundredths
of
asemitone
(cents).
If
the entire piano
different settings
of
the pointer.) has been tuned to equal temperament
(without
stretch)
Now
refer
to
illustration 7. Notice
that
the tuning
on
this lower pitch standard, then all strings would pro-
scale is calibrated
in
hundredths
of
asemitone (referred
~uce
stationary patterns
with
the
pointer
at
"-20."
to hereafter
as
"cents,"
that
is,
l/lOOth
of
asemitone=-l Obviously, any frequency in the range concerned will
cent, etc.).
Four
cents deviation from A-440
is
equal to always be
within
50
hundredths
of
asemitone from
approximately 1vibration
per
second as indicated by the some note
of
the standard scale.
(Table
1.)
To
learn
diagram.lTherefore,
if
it
is desired to tune the piano to
how
much
is
its deviation,
it
is
only necessary to turn the
A-445, move the
pointer
to the
right
to plus 20, 5(vibra- knob to the
right
or
to the left until the appropriate
tions) X 4 (cents
per
vibration}=20
cents,
or
for A-435
pattern
stands still.
The
only
judgment
lies in deciding
move
the
pointer
to
left
to
minus 20, etc. Figure 7shows when the
pattern
is
stationary.
No
comparison tone
how
the
pointer
would be moved to tune any
Ere-
is
ever sounded and all counting
of
beats
or
estimation
quency standard. Table
No.
1shows the deviation of
drift
speed
is
eliminated. Furthermore, deviations
settings for various pitches. can be read directly from asingle graduated scale which
Under
many circumstances
it
is
not
sufficient merely serves for all tones.
to
know
that
atone is sharp,
on
pitch,
or
flat.
It
is
While
the scale on the
Tuning
Unit
is
graduated
only
frequently very
important
to
know
how
much atone to 50
hundredths
of
asemitone, plus
or
minus, measure-
1
The
publication
"A
Table
Relating Frequency
to
Cents,"
by
ment
of
deviations
of
more
than
50
hundredths
of
a
Young,
is
available from
C.
G.
Conn Ltd. Price $1.00 semitone from aparticular note can readily be made
by
Figure
4-A-440.
Showing
pattern
of
the
fundamental
as
it
appears
in
4th
Octave
Band
of
the
"A"
window.
Figure
5-A-880.
Showing
pattern
of
the
fundamental
as
it
appears
in
5th
Octave Band
of
the
"A"
window.
PAGE
Six
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PATTERN
OF
FUNDAMENTAL
APPEARS
HERE
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-------:...---
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-
5.-/
......
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_____
TONE
SOUNDED
HERE +
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7
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r-
7TH
OCT.
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..
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5
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OCT.
-
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ST
OCT.
2ND
OCT.
3
RD
OCT.
4
TH
OCT.
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1=
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g<
-
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Ao
80
(,
0I
EI
F1
G,
A, 8,
(2
02
E2
F2
G2
A282
(3
03
E3
F3
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04
E4
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•
IE
(IU
OF
"ll
~
'"
til
'"
<
'"
Z
Figure
6-Shown
here
is a
drawing
of
a
piano
keyboard,
with
the
seven
octaves
separated*.
Lines
connect
the
octaves
with
the
corresponding
octave
band
in
the
Stroboconn
window.
For
example,
when
any
tone
in
the
first
octave
is
sounded,
look
for
the
pallern
in
the
first
octave
band.
Any
tone
in
the
second
octave
will
be
shown
in
the
second
octave
band,
and
so
on,
through
the
third,
fourth,
fifth,
sixth
and
seventh
octaves.
NOTE: See
text
for
special
instrudions
in
tuning
(R
and
all
tones
below
(4.
*For
the
purpose
of
this
manual,
the
octaves
01
the
piano
have
been
divided
as
follows:
First octave
includes
C1
through
8li
second
octave
C2
through
82,
etc.,
through
third,
fourth,
fifth, sixth
and
seventh
octaves.
STROBOCONN
"PIANO TUNING" MANUAL
Figure
7-Close-up
of
Tuning Scale,
with
pointer
set
at
zero,
or
A-440.
Small
numbers
indicate
where
pointer
would
be
set,
at
single
vibration
intervals, to
tune
to
an
"A"
of
any
desired
frequency
ISee Table
II.
Cents Frequency
From
A
From
Bb
Cycles/Sec.
+50
479.82
45 478.44
40 477.06
35
475.68
30 474.31
25 472.94
20 471.58
15
470.22
10
468.86
Bb 5467.51
+100
0466.16
- 5 464.82
-10
463.48
-15
462.14
-20
460.81
-25
459.48
-30
458.16
-35
456.83
-40
455.52
-45
454.20
+50
-50
452.89
45 451.59
40 450.28
35 448.99
30 447.69
25 446.40
20 445.11
15
443.83
10
442.55
5441.27
A0
-100
440.00
- 5 438.73
-10
437.47
-15
436.20
-20
434.95
-25
433.69
-30
432.44
-35
431.19
-40
429.95
-45
428.71
-50
427.47
Table 1
Cycles i
/Sec.
I
Cents
445
+20
444
+16
443
+12
442 + 8
441 + 4
A440 0
439 - 4
438 - 8
437
-12
436
-16
435
--20
Table
I-A
Tables I
and
l-A-Show-
ing Scale Pointer
settings
for
deviations
from
standard
sb
and
A.
PAGE
EIGHT
reading in aneighboring window.
For
example,
a
high
pitch A
of
457 cycles
per
second, which
is 66 hundredths
of
asemitone sharp, is read
in
the
A#
window, the reading being 34 hundredths
of
asemitone flat from A#.
To
aid players who play musical instruments
built
in
keys
other
than
C
and
who have
not
learned to transpose mentally, atransposition
indicator is provided, (See Fig.
2),
operated by
aknob
at
the
top
of
the Scanning Unit. An
opening
at
the left
hand
end
of
the mask under
"Instrument
In
Key
Of"
shows key
of
the
instrument,
and
the labels opposite each
of
the
twelve windows always correspond with the
written notes
for
that
instrument. For example,
if
an
Eb instrument is to be used, the pulling
of
the
knob
will change the label
at
the Eb
window to C, this being the written note that
must be played
in
order
to
produce astationary
pattern
in the Eb window.
At
the same time
the labels at each
of
the
other
windows will
similarly be changed to correspond with the
written notes for
an
Eb instrument. Provision
is made
for
transposition into all the commonly
used keys:
C,
Db, Eb, Fand Bb.
STROBOCONN
"PIANO TUNING" MANUAL
---"----
If
note
is
flat this
pallern
will
move
to
the
left.
Move
pointer
to left until
pallern
stops
and
read
exact
measurement.
If
note
is
sharp
this
pallern
will
move
to
the
right.
Move
pointer
to right until
pallern
stops
and
read
exact
measurement.
Figure
8-lnterpreting
Pallern
movement.
TUNING
THE
PIANO
Since the use
of
the Stroboconn
in
piano
tuning
has
become relatively widespread, we have found amarked
degree
of
similarity
in
the procedure followed
by
various
tuners who are using it.
After
consultin"g
with
numerous
wners, we find the following procedure more
or
less
typical:
PLACING
THE
STROBOCONN
IN
POSITION.
For
best and most rapid results, the Stroboconn should
be placed
on
atable, chair
or
stand,
in
aposition where
it can be most easily read while the piano is being tuned.
LOCATING
THE
MICROPHONE.
Both the air-
borne and contact microphones are available
with
the
Stroboconn.
The
airborne mike
i~
supplied with the out-
fit
and
the contact mike can be ordered as extra equip-
ment. Best results are obtained when the microphone is
located
as
close
as
possible
to
the string being tuned.
Most tuners place the airborne mike above the keyboard
of
the
piano,
and
shift
it
from time to time as they pro-
ceed
up
and down the scale.
The
contact microphone is
clipped to some
part
of
the piano which is found to be
carrying the
string
vibrations. (Experimentation may be
necessary.)
The
contact mike has an additional advantage, par-
ticularly when
it
is necessary
to
tune the piano where
there are
interfering
noises.
The
contact mike will pick
up
only the vibrations
of
the piano strings
and
other
interfering
noises will be somewhat suppressed.
It
has
also been found
that
the comparative advantages
of
the
two microphones differ with the individual piano.
TUNING
PROCEDURE. After the piano is prepared
for
tuning
with
the Strdboconn and its microphone
in
position, set the Stroboconn
pointer
at
the
proper
set-
ting
for
the standard
to
which the piano is to be tuned.
If
the piano is to be tuned to the Standard
Tuning
fre-
quency
of
A-440, set the
pointer
at zero.
If
it
is to be
tuned to some
other
standard, find the
proper
setting
in
,\\~
Figure
9-Stroboconn
mounted
on
portable
table
which
many
tuners
prefer.
Figure
10-Stroboconn
can
be
placed
on
any
convenient
chair,
on
a
piano
bench,
or
on
top
of
piano
iiself.
Several
other
setups
can
be
used,
depending
on
desires
and
facilities
of
the
individual
tuner.
PAGE
NINE
STROBOCONN
"PIANO TUNING" MANUAL
Figure
ll-Air-borne
microphone
located
on
piano
keyboard.
It
may
be
necessary
to
move
mike
several
times
in
order
to
obtain
maximum
reception
on
the
string
being
tuned.
Table
I-A
or
Figure
7.
For
example,
for
A-435, set
pointer
at
minus
20
and
for
A-442 set
pointer
at
plus 8.
Many
technicians
prefer
to
start
tuning
at
the
"break"
in
the scale because
of
the
marked
change
in
the
inhar-
mondty
of
the
partials
of
the tones
at
this
point.
The
stiffness
of
piano
strings
causes the tones
produced
to
have partials
that
are
not
harmonically related to each
other;
that
is,
the
second
partial
is
not
exactly twice the
frequency
of
the first partial,
or
fundamental,
of
the
tone.
The
third
partial
is
not
three times the frequency
of
the
fundamental,
and
so
on.
For
partials
to
be har-
monic they need
to
bear
awhole
number
relationship
(1,
2,
3, 4,----)
to
the
fundamental.
The
partials
in
piano
tones
are
always
slightly
higher
(sharp)
than
the
whole
number
multiples
(harmonics)
of
the
fundamen-
tal.
This
has avery
important
bearing
upon
the
tuning
of
apiano.
When
listening
to two
piano
tones an exact octave
apart,
the
second
partial
of
the
lower
tone
will
be
sharp
with
respect
to
the
fundamental
of
the
higher
tone.
This
will
cause audible beats to be
produced
and
the
listener
will
not
consider
the
tones
to
be
truly
an octave
apart
even
though
the
fundamental
frequency
of
the
top
tone
is exactly twice the
fundamental
frequency
of
the
lower
tone, as is
required
for
a
true
octave.
In
order
for
the
octave
on
the
piano
to
sound
in
tune
when
the two
no:es
are
played
at
the same time,
it
is necessary
to
lstretch
the
interval
by
lowering
the
bottom
tone
or
raising
the
top
tone.
The
technique
for
determining
the
optimum
amount
of
stretch
with
the
Stroboconn
will
be
explained
as we go
along.
The
inharmonicity
of
piano
tone
partials
is usually
smallest
in
the
middle
of
the
keyboard
so
an
octave is
chosen
there
for
setting
the
temperament.
Care
should
be
taken
that
the
"break",
or
a
marked
change
in
string
design, does
not
occur
within
the
temperament
octave.
All
but
one
string
per
key is
muted
with
felt
or
wedges so
only
one
string
at
atime
sounds
when
akey
is struck.
Let us assume
that
C4
(middle
C)
is chosen
for
the
starting
point
as
an
example. Some
other
starting
point
might
be
preferred
and
could be used as well. Proceed
from
C4
up
the
scale,
tuning
one
string
on
each key
while
watching
the
fourth
ring,
or
pattern
band,
in
the
appropriate
windows.
The
Stroboconn
pointer
is
left
in
the
position
chosen to establish
the
tuning
standard
while
tuning
this octave.
It
may
be
noted
while
tuning
this octave
that
even
though
the tension
on
the
string
is
adjusted
to cause
the
fo.urth
ring
pattern
to
be
stopped,
the
patterns
in
the
fifth
and
higher
rings
will
move slowly
to
the
right
due
to
the
fact
that
the partials
producing
those
patterns
are
not
exactly
in
a2, 4, 8-----
relationship
to be funda-
mental
of
the
tone.
If
the
fifth
ring
pattern
moves
to
the
right
for
the C4string,
when
the
fourth
ring
pattern
is
not
moving, ·the
tuner
can
note
how
far
to
the
right
he
needs
to
move
the
Stroboconn
pointer
in
order
to
make
the
fifth
ring
pattern
stand
still.
If
this is one cent
or
more,
it
indicates
that
Co
should
be
tuned
sharp
by
at
least
that
amount.
Therefore,
when
tuning
C,
the
point-
er
is advanced
to
the
right
of
the
s:arting
position
used
for
tuning
the
temperament
octave.
This
is the begin-
ning
of
the
octave-stretching process.
.
The
fundamental
is usually
the
strongest
partial
in
the
tones above
C4,
and
the
higher
partials
are progres-
sively weaker.
Thus,
the
fundamental
and
the second
partial
are
the
two
most
important
parts
of
the
tone
to
consider
when
tuning
octaves. However,
the
meticulous
Figure
13-"Stretching"
First
Octave.
To
"stretch"
the
first oc-
tave,
read
the
pattern
made
by
the
overtones
in
the
3rd
octave
band.
To
"stretch"
the
2nd
or
3rd
octave,
read
the
pattern
made
by
the
overtones
in
the
4th
octave
ba
nd.
PAGE
TEN
)0
Figure
14-"Stretching"
2nd
and
3rd
octaves.
STROBOCONN
"PIANO TUNING" MANUAL
lFigure
IS-Average
of
16
pianos
tested
by
Railsback
show
that
piano
tuners usually
tune
progressively
sharp
in
the
middle
and
high
octaves
and
progressively flat in
the
low. This
graph
is in-
tended
to
show
only
the
!tend
which
seems
to
be
followed
by
most
tuners.
It is
not
to
be
taken
as
a
pattern
to
be
followed
and
is
nol
to
be
considered
as
a
recommended
model
of
aperfect tuning job.
MISCELLANY
1.
.Lower
~C+ave
Patterns.
It
has previously been
explained
that
In
the
lower three octaves
of
the piano
the
fundamental tones are notoriously weak
WIth
their
strong
overtones. These weak fundamentals produce a
rather vague pattern,
of
short
duration,
in
the Strobo-
conn windows.
At
the same time,
the
overtones also pro-
duce their patterns
in
the various octave bands
of
the ap-
propriate
windows. As aresult, atuner using the Strobo-
conn
for
the
first time may be somewhat confused by
the
great
number
of
flashing patterns which appear when
the
lower octaves are tuned.
Because
of
the characteristics
of
the strings themselves,
the'patterns
in the lower octaves will never be quite
so
dear
and
distinct as those made by the strings in the
middle and
upper
octaves. However, as greater famil-
10.
1.
Railsback,
].
Acous. Soc. Am. 9:274
(1938);
10:86
(1938).
r::
7T
H
OCT.
t6TH
OCT.
t::::STH
OCT.
f=4
TH
OCT.
~
3
RD
OCT.
1=
2ND
OCT.
;=
1
ST
~
OCT.
-.30
-20
..
'0
o
iarity
with
the instrument
is
obtained, as aresult of
practice, the tuner will recognize
that
even
though
these
patterns are vague, they are clear enough, and
of
sufficient duration
to
make
an
accurate reading possible.
It
is
therefore advisable, because
of
the short duration
of
the patterns,
to
strike the strings more frequently while
tuning
the lower octaves so
that
the
pattern
will be re-
produced sufficiently
to
obtain
the
reading.
Also, since
it
may be desirable
to
stretch
the
lower
octaves
on
most pianos,
the
readings will be taken from
the
third
and
fourth
octave bands,
and
there will be
very few occasions
to
obtain the readings directly from
the first and second octave bands.
2.
"Stretched
OC+ave" Tuning.
It
is common
knowledge
that
there has been considerable controversy
and
discussion over "Stretched Octave" tuning.
It
is
not
the
purpose
of
this booklet
to
establish a
pattern
to
follow,
or
to
advise the tuner how he should tune the
oc-
taves with relation
to
each other.
Whether
or
not
the
up-
per
octaves should be
tuned
progressively sharp as
the
scale is ascended,
and
progressively flat as
the
scale is
descended, is a
matter
of
personal and individual taste.
It
is intended
to
emphasize, however,
that
by using the
Stroboconn,
the
octaves may either be stretched, tuned
to
the equally tempered scale,
or
tuned
to
any variations
from standard, as
might
be desired by
the
tuner
or
customer.
3.
Setting
the
Temperament. Before the commer-
cial availability
of
the Stroboconn,
tuner
and technician
were entirely dependent upon the ear
to
tune the custom-
ary temperament octave.
Although
the quality
of
the
work done by
the
skilled
and
experienced
tuner
reaches a
high
degree
of
excellence,
it
still requires acon-
siderable length
of
time
to
set an acceptable tempera-
ment
in this manner. Skilled piano tuners now find the
Stroboconn
an
invaluable aid which enables them
to
tune
the
temperament octave
to
an accuracy
of
one
one-hundredth
of
asemitone, in
as
little time as
it
re-
quires
to
tune any other octave. Equal temperament is
accurately established visually; however the amount
of
"stretching" required is best
de~ermined
visually and
aurally.
4. Microphone.
Two
microphones are available
for
use
with
the Stroboconn.
The
airborne microphone is
included
with
the Stroboconn
as
part
of
its standard
equipment,
and
the
contact microphone is available as
an
extra accessory.
It
cannot be stated definitely
that
either microphone
will give results superior to
the
other, in all cases.
The
airborne microphone has been found
to
be satisfactory
in
most cases,
but
on
some pianos
the
contact micro-
phone seems
to
do
abetter
job
in
the
extreme upper and
lower octaves.
It
is true, however,
that
in
all cases where
the
tuning
must be done
in
the
presence
of
outside and
extraneous noises,
the
contact microphone will help.
5.
Filter. Several years ago experiments were con-
ducted to develop alow-pass filter
to
be used
with
the
Stroboconn microphone. This filter was designed
for
use
under
circumstances where
it
might
be desirable
to
point
up
the fundamental patterns by eliminating the
overtones. Since
it
is necessary
to
tune
to
these overtones
when stretching octaves,
it
is therefore
not
desirable
to
eliminate them; so
that
the
USE
OF
THE
FILTER FOR
PIANO
TUNING
IS
NOT
RECOMMENDED, and
is
not
available.
PAGE
TWELVE
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