Rare Waves Grendel 2TAC User manual

2-Track Analog Control
For CV-Gate Music Synthesizers
Rare Waves LLC
RAREWAVES.NET

General Information
The Grendel 2TAC is a controller for music synthesizers that use the 1V/octave CV-Gate standard. It
requires patch cables with 3.5mm mono phone plugs, commonly used for Eurorack type systems.
Sequencer Standards
2TAC uses the pulse-per-step clock standard. One clock pulse advances the sequencer by one grid step.
Each clock pulse typically represents a 16th note or 8th note.
The sequencer has patchable Reset In / Reset Out connections to maintain a common reference point
when other sequencers are synchronized to it. A Reset Out pulse is transmitted when Stop is pressed.
While Reset In is activated, such as by patching a Gate signal to it, the transport is paused.
2TAC can serve as the master clock for other compatible sequencers, or it can be a slave unit to expand
your production setup when you’ve “maxed out” your other sequencers.
Pattern Data
2TAC’s patterns are limited to 4 different pitches. The 4 keys on the keypad can be considered as a 4-
note mini keyboard. You can tune the keys independently with the rotary encoders above each key.
The restriction of only having 4 pitches per pattern lends itself to a minimal compositional style.
However, it is possible to layer several patterns during playback with the Sticky Patterns feature. In this
case, you can produce sequences that contain more than 4 pitches.
Sequencing
You can easily create chains of patterns that play as a loop, allowing simple song structures.
But, 2TAC does not have extensive memory for lots of patterns, multiple song programming, or other
advanced DAW-like features. It is intended more as a scratch pad for developing musical ideas, and
performing minimal compositions which don’t involve a lot of pattern changes.
Controls One or Two Synthesizers
You can use 2TAC’s Track 1 and Track 2 outputs to play two different analog synthesizers, or use Track 2 as
an auxillary CV channel to control a single synth’s sound parameters like Filter CV, Velocity CV, etc. 2TAC
is not explicitly designed with the ACC GATE function, but you could use Track 2’s Gate Out for that
purpose.
Power Supply
Standard power supply is 9VDC, tip
positive.
It is OK to use a daisy-chain cable
to share power with other gear
from a single AC adapter.
It is safe to connect any DC power
source from 7.5 volts to 12 volts.
Polarity of the power source is
irrelevant. This unit accommodates
both tip-positive and tip-negative
AC adapters.
The unit is protected against over-
voltage with a built-in fuse (self-
resetting fuse).
Made by Rare Waves LLC
(Texas, USA)
RAREWAVES.NET
Design and Support:
Eric Archer
Manufacturer
Connections
V/OCT & Gate Out : 2 each
Clock In, Clock Out (5V pulse per step)
Reset In, Reset Out (5V pulse)
DIN Sync: Not supported
MIDI: Not supported

Keypad
Key I Key II Key III Key IV
CV-Gate Outputs Tuners
0V : Gate Off
+5V : Gate On
1V / octave
0 .. +5V Range
Gate OutV/Oct Out

Transport
Stop Play
Sync I/O Internal
Clock
1 pulse per step (+5V, rising edge triggered)
CLK OUT
CLK IN
Only when Transport is Playing. Also acts as Clock Thru.
+5V Gate or Pulse. Pauses transport and resets sequencer
RESET OUT
RESET IN
Transmitted when Stop is pressed
Active unless
CLK IN is patched

Mode Switch
Metronome
(Click Track)
Function Buttons

Mode Switch
The Mode Switch is the master control. Use it to choose what the Keypad and Tuners do.
The Mode Switch also works as an Undo for edits. While the EDIT LED is ashing, simply turn the Mode Switch to any other position,
and any edits in progress will be discarded. This also restores the tuning settings of all patterns to their last saved values.
The Keypad and Tuners control CV-Gate output on Track 1.
The Key LEDs light up with the sequenced notes on Track 1.
Press the Keys to play Track 1’s CV-Gate outputs in real time.
Use the Tuners to adjust the pitches of Track 1’s Keys
The Keypad and Tuners control CV-Gate output on Track 2.
The Key LEDs light up with the sequenced notes on Track 2.
Press the Keys to play Track 2’s CV-Gate outputs in real time.
Use the Tuners to adjust the pitches of Track 2’s Keys
1
The Keypad and Tuners control patterns for Track 1.
The Key LED lights up above Track 1’s actively selected pattern.
Press the Keys to switch between patterns on Track 1.
Use the Tuners to pitch transpose the the patterns on Track 1.
The Keypad and Tuners control patterns for Track 2.
The Key LED lights up above Track 2’s actively selected pattern.
Press the Keys to switch between patterns on Track 2.
Use the Tuners to pitch transpose the patterns on Track 2.
2
1
2

In mode, the tuners change the pitches of the Keys
Reset a key’s pitch to mid-range
(~ 2.5 volts)
Restore saved tuning settings
Change a key’s pitch by semitones
(0.083 volt per click)
Turn the tuner 1 click.
If you’ve reached the limit, the audible indicator sound changes.
Change a key’s pitch by octaves
(1.00 volt per click)
Hold the tuner down while turning it 1 click.
If you’ve hit the limit, the audible indicator sound changes.
Copy a key’s pitch to another key Press and hold the tuner of the source key while double-tapping
the tuner of the destination key
Save tuning changes to memory
Press and hold the tuner while tapping STOP
Tuning the Keys
2TAC’s V/OCT outputs are quantized in steps of 1 semitone equal temperament, or 0.083
volts. The pitches of the notes in your sequenced patterns can be adjusted with the Tuners
(rotary encoders) above the Keys.
2TAC has a tuning range of about 5 octaves. The voltages at its V/OCT outputs can cover
the range of 0 to +5 volts.
2TAC does not have provision for fine-tuning its V/OCT outputs. To make small
corrections to pitch, use the Fine Tune knob on the synthesizer you’re controlling.
Keys
Tuners
Hold EDIT so its LED ashes. Then hold EDIT again so the LED goes
dark. All tuning settings are saved to memory.
Hold EDIT so its LED ashes. Then turn the Mode Switch to any
different position. Previously saved tuning settings will be restored.
After you’ve made some tuning changes, and you’re happy with the results, remember to save them to memory by holding EDIT twice.
Otherwise, next time you undo any edits, the tuning changes will be lost also.

In mode, the Tuners change all notes in a pattern by an equal amount.
Transpose a pattern by 1 semitone Turn the tuner 1 click
Transpose a pattern by 1 octave Hold the tuner down while turning it 1 click.
Copy a pattern’s Key tunings
to another pattern
Press and hold the tuner of the source pattern, while double-tapping
the tuner of the destination.
Reset a pattern’s transpose
amount to zero Hold the tuner down while tapping STOP
Transposing Patterns
To make melodic composition more facile, you can easily transpose patterns.
Each pattern key has its own tuner, so you can transpose patterns in the
background while another pattern is playing.
2TAC’s transpose function can’t make its V/OCT outputs go beyond the range of
0 to +5 volts, so if you apply large transpositions to a pattern, the melodic
relationship between its notes will be affected. Normally, its suggested to keep
the transpose amount within +/- 1 octave.
Use the Coarse Tuning adjustment on the synthesizer you’re controlling to
optimize its pitch range.
Keys
Tuners
Restore last saved tuning
Save tuning changes to memory Hold EDIT so its LED ashes. Then hold EDIT again so the LED goes
dark. All tuning settings are saved to memory.
Hold EDIT so its LED ashes. Then turn the Mode Switch to any
different position. Previously saved tuning settings will be restored.
After you’ve made some transpositions, and you’re happy with the results, remember to save it to memory by holding EDIT twice.
Otherwise, next time you undo any edits, the transposed patterns will revert to their last saved values also.

Pattern Playback
Each track has memory for 4 patterns of 32 steps maximum. There are 3 memory banks - read on to learn how to switch memory banks.
Track Cue
The CUE buttons are used to mute / un-mute the tracks during playback.
When a track is muted, its CUE LED is dark. But its patterns continue to count in the
background, preserving the position of the downbeat.
Use the CUE buttons to insert drop-outs, fills, or to add white space or silent sections to your
compositions.
While a track is muted, you can hold the Keys to make its patterns play momentarily.
Jump cut Tap a Key while the sequencer is playing. It immediately switches to the newly selected
pattern.
In mode, the Keys switch between stored patterns, with options:
Cued transition Hold LOOP while tapping a Key. The sequencer will play to the end of the currently
active pattern, then switch automatically at the end of the bar.
Sticky patterns
(Pattern layering)
Hold PLAY while tapping a Key. The LED above it ickers while it is Sticky.
You can toggle Sticky status On/Off for each Key.
Notes of Sticky patterns are sounded in the blank steps of the active pattern.
Sticky patterns remain selected even if you switch active patterns or use Pattern Chain.
Momentary play Mute a track by pressing its CUE button so its CUE LED goes dark. Now you can tap
the Keys to play the patterns, but playback will only be heard while a Key is held down.
You can use the Tuners to transpose the pitch of a pattern at any time, even if the pattern is not actively playing.
All of the patterns are counting in the background, so you can jump cut between them without losing the position of the down beat.
Sticky patterns cancel All Sticky patterns are cancelled when you press STOP.
To cancel them without stopping the transport, hold PLAY and tap STOP.

Hold
To adjust the Metronome’s clock divider factor, hold CLICK while tapping Key I - Key IV
+ Tap:
1 2 3 4
Click Track (Metronome)
2TAC has a built-in audible metronome function. Tap CLICK to toggle the metronome On and Off.
The metronome automatically shuts off when you press the Stop button.
The metronome’s rate can be set to divide the clock by 1, 2, 3, or 4. The default on power-up is divide-by-4, or
quarter note beats if the clock input is considered 16th-notes.
Audible Indicator
The unit’s built-in speaker makes a variety of click sounds as confirmation of user input.
The tone of the click changes to indicate context.
* There is no way to turn off the audible indicator.

Pattern Chains
Chain Restore Hold LOOP and turn Mode Switch before releasing LOOP. The last chain is restored.
Patterns can be linked together into chains up to 32 patterns length.
A Pattern Chain can play through only once and remain on the last pattern in the chain. Or, you can make it repeat as an endless loop.
Pattern Chains can be programmed any time, whether the transport is playing or stopped.
The Transport LED ickers whenever a Pattern Chain is active.
“Greyed-out” Key LEDs indicate the patterns which are contained in the chain.
In mode, hold the LOOP button while tapping the Keys to create a pattern chain. Here are all the options:
Cued transition Hold LOOP while tapping one Key, then release. The sequencer will play to the end of
the currently active pattern, then switch automatically at the end of the bar.
Pattern Chain
- Single play
Hold LOOP while tapping a sequence of Keys. When LOOP is released, the Pattern
Chain begins. The Transport LED ickers until the Pattern Chain has played out.
Pattern Chain
- Endless loop Hold LOOP while tapping a sequence of Keys, then tap EDIT before releasing LOOP
Momentary Override
of Pattern Chain
While a Pattern Chain is running, press any Key to jump to a different pattern. As soon
as you release the Key, the sequencer returns to the Pattern Chain.
Hold
Write Pattern Chain
to Both Tracks
While holding LOOP, input a pattern chain by tapping the Keys. Then, tap the CUE
button of the other Track before releasing LOOP. The Chain is applied to both Tracks.
Chain Cancel Hold LOOP, then release it without tapping any other keys. Returns to normal playback

In mode, while the transport Is playing, use the LOOP and CUE buttons to control Temporary Loop Points.
Temporary Loop Points
Set Temp. Loop Point
on Track 1
While the transport is playing, hold LOOP while tapping CUE1 once. A temporary
loop point is added to Track 1 in real time.
Set Temp. Loop Point
on Track 2
While the transport is playing, hold LOOP while tapping CUE2 once. A temporary
loop point is added to Track 2 in real time.
Clear Temp. Loop Point
on Track 1
While the transport is playing, hold LOOP and STOP while tapping CUE1. Track 1’s
pattern returns to its original programmed loop length.
Clear Temp. Loop Point
on Track 2
While the transport is playing, hold LOOP and STOP while tapping CUE2. Track 2’s
pattern returns to its original programmed loop length.
You can change the loop point of a pattern to make it shorter with Temporary Loop Points.
Clearing a Temporary Loop Point restores the pattern to its original programmed loop length.
This feature lets you add variation to your patterns without having to edit them.
This function is only accessible with the Mode Switch on KBD1 or KBD2, and while the transport is playing.
Temporary Loop Points can be set for either Track 1 or Track 2, regardless of whether the Mode Switch is on KBD1 or KBD2.
The LED over the CUE button blinks dark when a Temporary Loop Point is reached.
Hold
Tap

Pattern Tools
2TAC includes useful functions for copying, time stretching, rotating, and modifying patterns.
Turn the Mode Switch to PTN 1 to modify Track 1’s patterns. When the Mode Switch is set to PTN 2, you can affect Track 2’s patterns.
* The Stop button has alternate functions in Pattern Tools mode. Pressing Stop while the EDIT LED is ickering will not stop the transport.
In mode, hold the EDIT button once. Its LED will icker to indicate Pattern Tools is in use. Here are all the options:
Pattern Copy
Hold the Key of the source pattern while double-tapping the Key of the destination
Pattern Copy
+ Timestretch
While holding the Key of the source pattern, turn its Tuner knob to change the time stretch
factor, then double-tap the Key of the destination. The copy will have a different time scale.
Pattern Rotate
While holding a Key, tapping the CUE1 (<<) button shifts all events in the pattern to the left
Each tap of the CUE2 (>>) button shifts all events in the pattern to the right by one step.
This is useful if you want to re-align a pattern to the rhythm down beat.
A nice trick is to create a rotated copy of a pattern, then jump-cut between it and the original.
Pattern Erase Transport must be stopped. Hold STOP and double-tap the Key of the pattern to
erase. Any note events will be cleared, but the loop length and tuning are preserved.
Over-write Pattern
with Random Data
Hold STOP + PLAY simultaneously, while double-tapping a Key. The pattern will be
replaced with random events, random loop length, and random tuning settings.
Copy Pattern
to Other Track
Hold Key of source pattern + LOOP while double tapping CUE1 or CUE2. The
pattern will be copied to same Key on the other track. (Can’t undo this operation)
Hold
Undo Turn the Mode Switch to a different position. Changes will be discarded.
Save and Exit Hold the EDIT button again, so its LED goes dark

Pattern Write - Real Time Edit
Add Note Events
Play the Keys in real time to over-write existing note events
You can record a pattern in real time by performing the events on the Keys. Your live input is quantized to the grid of the clock input.
To write a pattern on Track 1, follow these steps:
First, select the pattern you want to edit. Turn the Mode Switch to PTN1 and look at the Key LEDs. The bright LED is is the pattern that will
be edited. To choose a different pattern for editing, tap a different Key. Audition the patterns with the Play and Stop buttons.
Then, turn the Mode Switch to KBD 1 and press Play to start the transport. Now hold the EDIT button to enter Real Time Edit.
If the Click track is enabled, it sounds a double-click every time the pattern’s loop point is reached, providing an audible reference point.
* If a Pattern Chain is active, Real Time Edit will affect all the patterns in the chain as they appear during playback. Results can be unpredictable.
Hold while transport is playing
In mode, while the transport Is playing, hold the EDIT button to enter Real Time Edit.
Erase Notes
Hold LOOP(rest) while pressing a Key to erase events on that Key in real time
Undo Changes
Turn the Mode Switch to another position. Any edits will be discarded.
Save and Exit
Hold the EDIT button again so its LED goes dark. Any changes are saved to memory.
Switch to Step Edit
Press Stop. Playback stops, and you are now in Step Edit mode at Step 1 of the pattern.
Nudge Loop Point
Hold LOOP and tap CUE1 (<<) to shorten loop by 1 step, CUE2 (>>) to lengthen
Reset Loop Point
Hold LOOP while tapping STOP to reset pattern length to 32 steps
Set Loop Point
Double-tap LOOP to set the pattern’s loop point in real time

Pattern Write - Step Edit
Set Loop Point
Double-tap LOOP to set the pattern’s loop point at the current step
This feature lets you edit a pattern step-by-step for finer control of the note data. There are two types of note events: Trigger and Gate (Tie).
Trigger - Back-to-back Trigger events make a series of On-Off pulses at Gate Out, re-triggering the synth’s envelope generator.
Gate (Tie) - Gate Out remains on steadily during back-to-back Gate events. The synthesizer’s envelope generator will not re-trigger.
Hold while transport is stopped
In mode, while the transport Is stopped, hold the EDIT button to enter Step Edit.
Step navigation
Jump to Step 1
Press Stop
Navigation
Tap CUE1(<<) to move back one step. Tap CUE2 (>>) to move forward one step.
Trigger events are shown by a momentary LED. Gate events have a steady LED.
The Audible Indicator makes a double click sound when you pass Step 1.
Add Trigger Event
Add Gate (Tie) Event
Tap a Key
Hold a Key
Erase Event
Double-tap the Key whose LED is lit
Reset Loop Point
Hold LOOP while tapping STOP to reset pattern length to 32 steps
Undo Changes
Turn the Mode Switch to another position. Any edits will be discarded.
Save and Exit
Hold the EDIT button again so its LED goes dark. Any changes are saved to memory.
Switch to Real Time Edit
Press Play. Playback begins and you can listen to your changes, and edit in real time.
Nudge Loop Point
Hold LOOP and tap CUE1 (<<) to shorten loop by 1 step, CUE2 (>>) to lengthen.

Bank 2 Bank 3
Select Memory Bank
Bank 1
Hold Key I, Key II, or Key III for 2 seconds after applying power to the unit, as soon
as you see its LEDs light up.
Immediately after powering up the unit, use Key I - Key III to select the active Memory Bank.
Over-write Memory Bank
with Random Data
Power cycle the unit. As soon as the LEDs come on, hold STOP + PLAY and Key I, Key
II, or Key III simultaneously. The display ickers, and all data in the selected bank is
replaced with randomly generated note events, random pattern lengths, and random
tuning settings.
Memory Bank Select
2TAC has three memory banks for pattern storage.
The actively selected memory bank is indicated at power-up by a ashing LED over Key I, Key II, or Key III.
After switching memory banks, any Pattern Chains will be lost.
To power cycle the unit, unplug the DC Input from the back of the unit for several seconds, then plug it back in.

How Can I ... ?
Set a pattern’s loop length exactly:
1. To adjust a Track 1 pattern, set the Mode Switch to KBD 1
2. If the transport is playing, press STOP
3. Hold EDIT to enter Step Edit mode
4. Reset the pattern’s loop length to 32 steps by holding LOOP while tapping STOP
5. Think of the number of steps you want your pattern to have. For example, lets say it is 8
6. Tap STOP while thinking the number “1”. You’ll hear the audible indicator click
7. Now tap CUE2(>>) while counting up “2, 3, 4 ...” as you go. After you get to “8”, double-tap the LOOP button.
8. The pattern length is now set to 8 steps. Hold EDIT again to exit and save
Start a new pattern from a blank:
1. To erase and over-write a Track 1 pattern, set the Mode Switch to PTN 1
2. Hold EDIT to enter Pattern Tools mode
3. Hold STOP while double-tapping a Key to erase its pattern
4. Cancel any transpose settings by holding the key’s Tuner down while tapping STOP.
5. Hold EDIT again to exit Pattern Tools and save the changes.
6. Now turn the Mode Switch to KBD 1.
7. Audition the pitches of the Keys by playing the keypad and adjusting the tuners according to the melody you have in mind.
8. Next, set the pattern’s loop length (see above) to match your new idea
9. Use Real Time edit or Step Edit to program your new pattern. If you’re using Real Time edit, turn on the click track to help keep rhythm.
10. Be sure to hold EDIT again to exit and save - if you turn the Mode Switch before doing this, you’ll undo your changes!
Make Track 2’s patterns match Track 1’s:
When you’re using Track 2 as the auxilliary CV channel for a synth that’s controlled by Track 1, you may want to keep Track 2’s patterns in sync
with Track 1’s.
1. For all 4 patterns, copy Track 1’s data to Track 2 using the Copy Pattern to Other Track procedure in Pattern Tools.
2. Now Track 2’s patterns will have the same events and loop length as Track 1’s.
3. Transpose and Re-tune Track 2’s patterns as desired to produce the auxilliary CV output.
4. If you’re using Track 2’s Gate Out as ACC Gate for your synth, edit the Track 2 patterns to delete note events wherever you don’t want an ACC.
5. When you program a Pattern Chain, use the Write Pattern Chain to Both Tracks procedure in Pattern Chain.

KEYS
PATTERNS
Hold
Hold
Hold
Press Press
Playing
Hold
Memory Banks I-III
Current Memory
Bank is indicated at
power-up by ashing
LED over Key I-III
Switch Bank:
Unplug power, then
hold Key I-III while
re-applying power.
Overwrite a Bank
with Random Data:
At start-up, hold
STOP + PLAY +
Key I, Key II or Key III
Exiting Pattern Tools
Save changes:
Hold EDIT again
Undo Edits:
Turn Mode switch
LIVE KEYS
KEY TUNERS
TRANSPOSE
PATTERN SELECT
Mode Switch
Track 1 Keys
Track 2 Keys
Track 1 Patterns
Track 2 Patterns
Pattern Copy:
Hold Key of source while double-tapping Key of destination
Pattern Copy + Timestretch:
While holding Key of source, turn its tuner to change the time stretch factor,
then double-tap key of destination
Pattern Rotate:
While holding Key, tap CUE1 (<) or CUE2 (>) to shift pattern events.
Pattern Erase: (only when transport is stopped)
Hold STOP while double-tapping a Key
Overwrite Pattern with Random Data:
Hold STOP + PLAY while double-tapping a Key
Copy Pattern to Other Track: (can’t undo this)
Hold Key of source + LOOP while double-tapping either CUE1 or CUE2.
Change patterns at the end of the measure: Tap one Key then release LOOP
Add multiple patterns to the chain: Tap Keys I-IV in order, up to 32
Song Loop (endless chain): Tap EDIT before releasing LOOP
Apply chain to both tracks: Tap the Cue button of the other Track
Chain Cancel: Release LOOP without tapping any other buttons
Restore Last Chain (undo): Turn Mode switch before releasing LOOP
Stopped
Playing
Pattern Tools
Pattern Chain
Step Edit
Temporary Loop Points
Real Time Edit
Set temporary loop point: Tap CUE1 or CUE2 to loop the track’s pattern
Clear temporary loop point: Hold STOP while tapping CUE1 or CUE2
While transport is playing, hold the LOOP button down, then...
While holding LOOP button down...
until LED ickers
I II III IV
I II III IV
I II III IV
I II III IV
Tap a Key to select pattern I - IV
Immediate jump cut while playing
Play the V/oct & Gate outputs
in real time like a 4-note keyboard
Event Write: Play keys to write notes in real time
Event Erase: Hold LOOP(rest) while pressing keys
Nudge Loop Point: Hold LOOP and tap CUE1(<<) or CUE2(>>)
Reset Loop Point: Hold LOOP and tap STOP to reset pattern length to 32 steps
Navigation: Use CUE1 (<) and CUE2 (>) to navigate forward and backward
Jump to Step 1: Tap STOP
Note Write: Tap Key to add a Trigger event. Hold Key to add a Gate event
Note Erase: Double-tap Key to erase an event on the current step
Make Loop Point: Double-tap LOOP to set the loop point at the current step
Nudge Loop Point: Hold LOOP and tap CUE1(<<) or CUE2(>>)
Reset Loop Point: Hold LOOP and tap STOP to reset pattern length to 32 steps
Default: 1 semitone per click
Hold & turn: 1 octave per click
Tuning copy:
Hold tuner of source pattern,
double-tap tuner of destination
Transpose Reset:
Hold tuner and tap Stop
LOOP
rest
LOOP
rest
EDIT
save
EDIT
save
Tune the keys (adjust V/oct voltage)
Pitch shift all the notes in a pattern
Default: 1 semitone per click
Hold & turn: 1 octave per click
Pitch Copy:
Hold tuner of source,
double-tap destination tuner
Pitch Reset: (middle of range)
Hold tuner and tap Stop
Exiting Edit Mode
Save changes:
Hold EDIT again
Undo Edits:
Turn Mode switch
until LED ickers
Keypad and Tuners Edit and Loop Buttons Memory
Hold Play + Tap Key I-IV to make
Sticky patterns (they play in white space of active pattern)
Hold Play + Tap Stop to clear Sticky patterns