SQ-4M - Eurorack multi track MIDI step sequencer

SQ-4M is a software to run on the VMC-system. It provides a MIDI step sequencer with 16 parallel monophonic tracks, inspired by the sequencers in the Roland JX-3P and SH-101. The software is published as open source under the creative commons license "by-nc-sa 4.0"

• Download the Version 0.29 of the Arduino code
• This software is a beta-version. There is no warranty on it!
  --- AFTER UPLOADING A NEW FIRMWARE always do a FACTORY RESET in the setup menu; when upgrading from Versions below 0.17 do also a POTENTIOMETER ADJUSTMENT one time. ---

This is a sound example which was created using the SQ-4M. Basically this is a single repeated F-maj7 chord played over three octavas like A3, C4, E4, F4, A4, C5, E5, F5, A5, C6, E6, F6, A6. It becomes a "piece of music" by the function clock division that determines for each of the 12 notes how many clock ticks happen until the note is played the next time. Think it a A3 on every step, C4 every second step, E4 every third step and so on. I unmute one track after the other, beginning with C4 (A4 is left out).

Additionally there is a simple bass figure played by an acoustic upright bass.
A random function sets for each note a different velocity value.
Finally I transposed all tracks sometimes.

Astonishing enough this does not sound like invented from a machine.

The sounds for the piano and the upright bass come from a Roland SC-33 soundmodule.

SQ-4M - Users Manual

Firmware Version 0.29
VMC-1 Hardware Version 1.5.4

"SQ-4M" is a programm for an Arduino Nano mounted on a " fanwander VMC-1 ". The SQ-4M is a MIDI step sequencer which can be triggered by external positive voltage trigger signals, by an internal clock, by DIN-Sync or by MIDI-Clock. The SQ-4M provides 16 single event tracks with 64 steps per track, where each step can have a length of 8 bars (if you read the incoming trigger as 16th notes).

The event can be either

• a MIDI note,
• a MIDI ControlChange command
• a velocity value for another note-track
• a transpose value for another note-track.

Each track can have

• a different step length,
• a different clock-tick-per-step ratio.

This is valid for the transpose or velocit tracks too. So you can have a 12 note sequence with a velocity pattern that repeats after 5 steps, but each step takes 3 steps of the note sequence and a transposition sequence which has a steplength of four bars, and ... and ... and. The posssible combinations are endless.

Usually you will buy a fanwander VMC-1 with the software installed already. If your VMC-1 runs a different software at the moment, then please consult the programming instructions for the VMC-1 on how to install software.

Quickstart...

...for those, who think they don't need manuals:

• The function of the five buttons
  
  

  	START *)	STOP	WRITE	F1	F2
  Stop Mode	Play		Write	Enter SETUP
  		Delete Sequence	<--Hold
  		Hold-->	MIDI-Reset
  	-- track ++				<--TRACK SELECT
  	unmute all	mute all		<--ALL TRACKS	(transpose)
  Play Mode	Pause	Stop	Write	Enter Setup
  	-- Track ++				<-- TRACK Select
  	unmute all	mute all		<-- ALL TRACKS	(Transpose)
  Write Mode	End & Play	End & Stop	Back	Tie for note tracks Enter for cc tracks of velocity tracks	Rest
  Setup Mode
  Select Param	Exit Setup		Edit	< Parameter >
  	TRACK Select -->			-- Track ++
  Set Param		HOLD and select with CV2	Set	-- Value ++

  *)On the first run of modules this button is labled "PLAY", in the later runs the button will be labled "START".
  
  
• Good Luck :-)

Now more details for the patient ones...

Connect and Configure the Hardware

This is described in the users manual of the VMC-1.

MIDI connections

Basically you need a device which sends MIDI-notes (I will call this "the keyboard") and a device which can create sounds from MIDI-notes (I will call this "the synth"). I will not explain how to connect MIDI devices. So establish the following MIDI connections
Keyboard-MIDI-Out <-> SQ-4M-MIDI-In,
and
SQ-4M-MIDI-Out <-> Synth-MIDI-In.

Usually you will get a VMC-1 with the SQ-4M software loaded, and set to factory settings. To test with the factory settings of the SQ-4M, set keyboard and synth to MIDI channel "1".
For other settings please consult the description of the "setup menu".

Press PLAY. The sequencer should play on the synth a repeating F-major-7 chord of 14 notes and you should be able to play the synth on the keyboard along with the sequence (at least as long as your synth is polyphonic).

If the sequencer plays other notes than the repeating F-major-7 chord then please do a "Factory Reset" as described in the section "setup menu", and follow the instructions for "Adjust Poti-CVs" in the section "setup menu" after the factory reset.

Selecting Tracks

The SQ-4M provides in the default configuration 16 distinct tracks. Many functions are available for each track separately, and some functions are valid for all tracks.

• To select a track in play mode or stop mode, press and hold the F2 button and flip through the tracks using the START and STOP buttons.
• To select a track in the setup mode, this works the other way around: press and hold the START button and flip through the tracks using the F1 and F2 buttons. (this opposite handling may feel confusing, but it is quite logical from the use of these buttons in the setup mode).
• It is not possible to select a track in write mode. You have to select the track in stop mode or play mode and enter the write mode then.

Write Mode

We assume you can play the default sequence successfully and your keyboard plays notes on the synth.

Writing a Sequence in the SQ-4M - Basics (Write a Note Track)

• If the sequencer is running hit the STOP button. (_{you may change to WRITE mode also, while the sequence is running, but for now it is easier to do this in STOP mode.})
• Press and Hold F1 and press STOP to mute all tracks
• The Display should look like this:

  STOP        Tr1 all tracks muted

• The display tells us, that we are in stop mode and track 1 is selected.
• Hit the WRITE button.
  => the display says "WRITE" (who would guess...)
• Play a few single notes on your keyboard. Be sure not to overlap notes.
  => you should see on the display the counter in the upper line count up with each note. Also you should see the recorded MIDI note number and in the lower line a "+"-character for each step.

  WRITE #49     4 ++++

• Hit PLAY.
  => the SQ-4M will play the notes that you've entered before.

The WRITE-mode ends either if you hit STOP or PLAY or it ends automatically if you reach the track length limit.
* If you write a track while the sequence is running and you end the WRITE-mode with STOP, then the sequence will continue running, but the current track will be in pause mode. If you end the pause mode by pressing PLAY the current track will start playing on the next bar
* If you write a track while the sequence is running and you end the WRITE-mode with PLAY, then the current track will start with the next bar

The sequencer can store up to 64 steps. A step is written, as soon as you press the key down on your keyboard. Even if you play more than one keys without releasing the first one always a new step is written with any new keypress

Writing will keep a sequence only in the runtime memory. Unless you save the pattern the entered sequences will be lost after a powering off or reset as it happens after uploading a new firmware.

To store the sequence permanently on the EEPROM, you have to use the functions SAVE and LOAD in the setup menu. If you want to use this Arduino board for other applications please obey the remarks in the chapter about -> setup -> save/store.

Write Mode extended - tied notes and rests

Lets write now a four note phrase.
Select an organ like sound at your synth. Take care, that there is no long "Release" on the sound.

• Press WRITE
• Play Key C
• Press F2 (=REST)
• Play Key C
• Press F1 (=TIE)
• Press STOP

• Press PLAY

The sequence will play something like "Dap, Daaaah, Dap, Daaah,...."
Do the same with A.A-C.C-A.A-E-G- and sing "Fly, Robin, Fly".

Write Mode extended - Correcting Steps

There is no real editing of a sequence for now (it may be possible in a later firmware version), but while writing you can step back by hitting the WRITE button for each step back. Example:
We want to enter a Cmaj scale, but hit G# instead of G:

• WRITE
• C
• D
• E
• F
• G#
• A ... Aaargh, Hold it! The G# was wrong...
• WRITE (will step back and clear the A)
• WRITE (will step back and clear the G#)
• G
• A
• B
• C
• STOP
• PLAY

Check the step counter and the "+++..."-step-display-line while stepping back.
I think you 've got it.

Write Mode extended - Cancel Write!

Sometimes it happens (at least to me), that you press WRITE, though you did not want to write a new sequence. In this moment you have the chance to cancel the write-mode (and keep the existing sequence), by pressing WRITE again. But it is important, that no MIDI-NoteOn came in meanwhile and that you did not hit TIE, REST, PLAY, or STOP. As soon as one event happens, that the write-mode would record, the former sequence is gone.

By the way: it is not possible to enter the write-mode while playing or while the setup. So the chance for this problem is quite low.

Write Mode - Write Values for CC-Tracks or Velocity Velocity Track

You can write a sequence of CC values or velocity values in multiple ways:

• be sure to have no cable plugged into the input CV2; use the knob CV2 to dial in the value and confirm with F1 Button
• (coming with Version 0.40:) hold the PLAY button and play notes on the keyboard within a range of one octave below and above the transposition center note. This will be more coarse than the method with the CV1 knob, but it is much quicker

Erase All Tracks - (Version 0.17 and higher)

Sometimes you may want to start a pattern from the scratch. That for use the following order of button presses:

• press and hold WRITE,
• press and hold STOP,
• release WRITE,
• release STOP.

This will write pauses on all steps of all sequences. The track length of all tracks will be set to 1. The track parameters like track type or out channels are kept.

Play Mode

Playing a written sequence is simple: hit PLAY. The sequence will play in the tempo of the tempo potentiometer (or external clock - if selected) and with the blinking LED. (The LED blinks always - even when the sequence is stopped). Hit STOP to end the play mode.

Play Mode - set Tempo

The SQ-4M provides an internal clock generator. The tempo-knob controls the speed of the clock.

Play Mode extended - Thru

While the sequence is playing, MIDI information from the keyboard may be forwarded to the output (so called Soft-Thru); this forwarded note will be sent on the MIDI channel of the selected track. The SQ-4M provides various thru-settings. For details see the setup section.

Play Mode extended - Transpose

The SQ-4M also provides the possibility to transpose the played sequence according to the incoming keyboard notes. There are four different types of TRANSPOSE: continous, momentary, button-enabled, and track. In the "track" transpose mode any other track can be used for transposition. Since the SQ-4M does not distinguish between values for notes, CC-values or velocity, any track may be used. A track can be configured as dedicated transpose track. The difference is, that transpose-tracks are not affected by the mute function, and they do not send MIDI note events. They are used only internally

The center note for the transposition (where no transposition happens) can be choosen in the setup. For details see the setup section.

Play Mode extended - external Trigger-In

This is the topic, where the SQ-4M is different to all other MIDI step sequencers, we know.
Please read now first at the chapter "Setup Mode" about the two different NoteOff modes

You may replace the internal tempo clock or MIDI-clock, by an external trigger signal fed to the CLOCK-IN socket. To speak more exact: this is handled as a GATE signal. The input expects a voltage of +5 Volt (=gate on) or 0 Volt (=gate off).
If the input rises from 0V to +5V the MIDI noteOn messages for the notes in the actual step are sent.
If the input falls down from +5V to 0V and the noteOff mode is set to "clocked", then the MIDI noteOff messages for the notes in the actual step are sent.
This means the length of the incoming "clock gate" determines the length of the played note.
(The gate signal may be higher than 5V, but gate off has to be 0 Volts)

What is that good for?

Example 1:
Have a drum machine like Roland TR-808 that sends continuous 5V-clocks.

• Connect the clock out of the drum machine with the CLOCK-IN of the SQ-4M.
• Press PLAY on the SQ-4M (the sequence will not play yet!)
• Start the drum machine

=> The SQ-4M will play in the tempo of the drum machine.

Example 2:

• Have a drum machine with progammable trigger out, like the Roland TR-606 or Roland TR-08 or many others.
• In the Setup reassure, that the "Note Off Mode" is set to "Held Note" (this is the default value from the factory - if you didn't change it until now, then go on)
• Write a sequence of four notes:
  G A C D
• In the drum machine set a trigger at the first step of a bar, but none on the other steps in the bar
• Hit PLAY at the SQ-4M and start the drum machine

=> The SQ-4M will play a four bar sequence, with changing notes at every bar and each notelength is the full bar.
If you would try this with a regular internal 16th clock, you would need 64 steps using the TIE function. Having the externally programmed trigger on step one, you have to enter only four steps.

Example 3:

• Have a drum machine with programmable trigger out, like the Roland TR-606 or Roland TR-08 or many others.
• Write a sequence of four single notes:
  D E G A
• In the drum machine set triggers at the following positions of a 4/4 pattern
  x.x.xx.x.xx.x.x. (x means a trigger, dot means no trigger)
• Hit PLAY at the SQ-4M and start the drum machine

=> The SQ-4M will play a sequence which will repeat not before 9 bars.
Now change the sequence to "D" "E" "REST" "G" "A" "REST" => I think you will get it.

Clock Division per Track

The three previous examples assume that each incoming clock tick triggers one step of the sequence. Each track has a parameter "CLOCKDIVIDER TR" (don't mismatch this with the global parameter "Clock Ratio"). With this parameter you determine how many clock ticks must come in to make this track advance to the next step. If you set the clockdivider to a different value for each track, you can get very complex sequences from very simple base tracks. Just one example: enter for each track two notes like this:
Track 1: C2 G2
Track 2: C3 G3
Track 3: H3 C4
Track 4: E5 D5
As long as the clockdivider has the same value on all tracks, this will be very boring. Now set the clockdivider like this:
Track 1: 2
Track 2: 1
Track 3: 3
Track 4: 5
The sequence will look like this:
Track 1: C2    G2    C2    G2    C2    G2    C2    G2    C2    G2    C2    G2    C2    G2    C2    G2    C2...
Track 2: C3 G3 C3 G3 C3 G3 C3 G3 C3 G3 C3 G3 C3 G3 C3 G3 C3 G3 C3 G3 C3 G3 C3 G3 C3 G3 C3 G3 C3 G3 C3 G3 C3...
Track 3: H3       C4       H3       C4       H3       C4       H3       C4       H3       C4       H3      ...
Track 4: E5             D5             E5             D5             E5             D5             E5      ...
Now it takes 60 steps until this simple two step sequence repeates.

Mute the sequenced MIDI while playing

If the sequencer is playing and you press START again, then the MIDI-Out will be muted. No NoteOn messages will be sent from the sequence. MIDI NoteThru will still work. The "PLAY" in the top line of the display will change to "play", but you will see in the second display line, that the sequence continues running.
As soon as you press START again, the display will change to "plAY" and beginning with the next step #1 of the sequence the NoteOn messages will be sent again (and the display will change back to "PLAY"). If you press START again while the display shows "plAY" then the sequence will be unmuted immediately.

If you want to mute all tracks at the same moment, press and hold F1 and press STOP (the sequence won't stop! Only all tracks will be muted). If you want to unmute all tracks at the same moment, press and hold F1 and press START.


If the sequence is stopped, then it depends on the setting of the track parameter "PLAY-ON-START" whether the initial Start command will unmute all tracks (setting "Play always"), or whether the muting status that was given when you stopped the sequence, will be kept (setting "Obey mute mode").
The muting will not affect the MIDI events provided by the MIDI-Thru functions!

A MIDI start command will not act as mute function, but if PLAY-ON-START is set to "Play always"

Velocity Control and Random Velocity

The velocity of the notes sent by the sequencer is basically fix, because the sequencer does not record the velocity value of the incoming notes. Depending on the global settings and the individual tracksettings the velocity comes either directly from the CV1-knob or from a random function, whichs amount is controlled by the CV2 knob, or from a dedicated velocity track

Shut up mode :-)

Under certain cirumstances it may happen that the synth produces "hanging" notes - even if the sequencer is stopped. To cancel these notes in play mode or stop mode simply press F1/TIE. This will send NoteOff messages for all 128 Notes, NoteOn with velocity 0 for all 128 Notes, and the All Notes Off CC #123 on the selected MIDI-out channel.
Pressing STOP in play mode sends also this kind of reset.

Shut up and reboot

Though software should be perfect, software never is perfect. So if this software hangs there exists a full system-reset:
pressing all five buttons at the same time will restart the program. Unfortunately the Arduino itself may hang. In this case you have either to power cycle your system, or press the reset button on the Arduino pcb.

Setup Mode

In the setup mode you configure the general behaviour of the SQ-4M and the individual tracks. You can enter the setup mode in play mode or in stop mode. In write mode the setup is not available.

1. To enter the setup menu press F1 and F2 together.
2. The display will change and list the current parameter in the upper line. The lower line will display the current value of the parameter.
3. To page through the parameters use F2 for "next" and F1 for "previous".
4. To change the value of a parameter press WRITE.
   => An exclamation mark ("!") will appear at the begin of the lower line to mark the EDIT mode.
5. Change the value with F1 (=decrease by one) and F2 (=increase by one), or hold the STOP button and dial the value with the CV2 knob (remove cables from the CV2 input before!).
6. Press WRITE again to leave the EDIT mode.
   => the value will be stored in the non volatile memory and the "!" disappears.
7. To leave the setup menu press PLAY and STOP together.

After a system reset or startup the setup starts always with "transpose mode". You may step through all parameters in a circle in the both directions.
On each following lookup of the setup menu, you will be placed in the menu, where you left the setup before.

If you are at editing the parameter of a track (step 5 in the list above), then you may page through the tracks and change the currently selected parameter there too.

If you have entered the setup mode while the sequence was playing, the sequence will continue playing, but you cannot stop it in setup mode. You have to leave the setup mode to stop a playing sequence.
Since the internal clock is software created and the setup mode eats up a lot of processing, the internal clock will assumingly become a little slower.

List of the available Parameters:

• "Transpose": switches between various transpose modes and off.
• "Noteoff Mode": switches between a gated note length and notelength until the next step.
• "Note Length": sets a minimum note length for the gated NoteOff mode.
• "In-Channel": sets the MIDI channel on which the SQ-4M expects incoming note data.
• "Out-Channel TR": sets the MIDI channel per track on which the SQ-4M sends its sequence.
• "Tracktype TR": sets the type of MIDI message which is sent by this track
• "CC-Number TR": sets the CC-Number which is sent, if the track type is CC.
• "Vel.Track TR": Not in use in Version 0.15.
• "Transp.Track": Not in use in Version 0.15.
• "Clockdivider TR": sets the clockdivider per track.
• "PlayOnStart TR": sets the mute behaviour of each track, when the sequence is started.
• "Note-Thru": determines under which conditions incoming notes from the keyboard are forwarded to the synth.
• "Control-Thru": sets whether incoming MIDI-ControlChange data are forwarded to the synth.
• "Program-Thru": sets whether incoming MIDI-ProgramChange data are forwarded to the synth.
• "Bend-Thru": sets whether incoming MIDI-Pitchbend data are forwarded to the synth.
• "OtherCh-Thru": sets whether MIDI-data on other channels than the out channel are forwarded to the MIDI out.
• "Copy Paste": allows copy and paste between tracks (still buggy in V 0.29 - sorry)
• "Adjust Poti-CVs": adopts the software for the real potentiometer values
• "Factory Reset": restores to the default parameter values and loads the test sequence
• "SaveSequence": saves the actual sequence in the EEPROM
• "LoadSequence": loads the sequence from the EEPROM
• "Clock Source": selects the clock source
• "Start/Stop Source": determines which source starts and stops the sequencer
• "Send Clock to...": determines whether the SQ-4m sends clock to MIDI and/or the VMC bus (Din-Sync)
• "Clock Ratio": determines the step ratio of the incoming/sent MIDI-clock or DIN-Sync-clock and the internal steps
• "Transp.Center": sets the note value, that corresponds to 'no transposing'

Now the detailled desciption of the parameters

Transpose (global)

Transpose shifts the pitch of the sequences played.

This parameter applies to all tracks that use "Global Transpose" as the transposition source.

The transposition refers to the "center note", which corresponds to "no transposition" and is set with a separate parameter. The default setting is MIDI NoteNumber 60 (C5). MIDI NoteNumber 62 = D5 therefor shifts the sequence up by a whole note, MIDI NoteNumber 53 = F4 down by a fifth.
If a transposition shift is effective, its amount is displayed in Play and Stop mode.

Transposition does NOT affect the notes played manually via MIDI Thru and has no effect on the notes stored in memory - it is only a playback function. Transposition is not active for the Thru notes in write mode.

Velocity (global)

This determines the velocity values or played sequences. This parameter is valid for all tracks which use the "global velocity" as velocity source.

Noteoff Mode (global)

The noteOff mode selects, what determines the outgoing noteOff. In play-mode this setup page can be reached directly by pressing the WRITE button.

In Channel

The MIDI-channel on which the SQ-4M expects the data, that shall be written into the sequence or shall be used for transposing

Out Channel (per Track)

The MIDI-channel on which the sequence of the corresponding track and thru'ed Program/Control/Bend-data are sent out.

Tracktype (per Track)

Sets the type of MIDI message, which is sent by the corresponding track

CC-Number (per Track)

If the track is a CC-track, then this value determines which ControlChange message is sent.

Velocity Source (per Track)

If the track is a Note-track, then this value determines which source controls the velocity value of the notes sent.

Transpose Source (per Track)

If the track is a Note-track, then this value determines which source controls the transposition of the notes sent.

Clockdivider (per Track)

This parameter sets how many clock ticks have to happen until the selected track advances to the next step.

PlayOnStart (per Track)

This parameter sets whether the corrsponding track begins to play always on a start command, or whether the current mute state is obeyed

Note Thru

This parameter determines under which condition note messages from the keyboard (= on the in-channel) are forwarded to the synth (= on the out-channel).

Control-Thru

Determines whether MIDI controlchange data from the keyboard (= in-channel) are forwarded to the synth (=out-channel)

Program-Thru

Determines whether MIDI Programchange data from the keyboard (= in-channel) are forwarded to the synth (=out-channel)

Bend-Thru

Determines whether MIDI controlchange data from the keyboard (= in-channel) are forwarded to the synth (=out-channel)

!!! Important Remark on Thru-Modes !!!

If you use the same device as keyboard and as synth then all those Thru-settings depend on your instrument.
If the instrument has a local-off mode, then you should activate this local-off mode and you should set all Thru-settings to "On" and the NoteThru not to "On". For example my Rhodes Chroma Polaris in local off mode needs ControlThru and BendThru set to "On". Otherwise the Chroma Polaris could not be edited. But ProgramThru has to be set to "Off". Otherwise a MIDI-Loop on program change commands would happen and bring the whole MIDI-system to hang.
If the instrument has not(!) a local-off mode then you MUST set all Thru-settings to "Off". Otherwise you would create an endless MIDI-loop which typically makes all processors overload and leave the system in unusable state, which typically can be solved only by switch off both the synth and the SQ-4M. The same is valid if you use the SQ-4M at the input and output of a MIDI-sequencer like Logic, Cubase, Ableton, Reaper, what ever...

OtherCh-Thru

Determines whether incoming MIDI data (no matter which type) in channels other than the out-channel are forwarded to the output.

Copy Track

This features copies the track-individual settings from one source track to a clip board and allows to paste those data into other track settings. A similar function is planned for the sequence values of the tracks.

Adjust Poti-CVs

Potentiometers are produced with a tolerance of 10% or even 20%. This function adopts the software to the individual potentiometers in this circuitry. This procedure has to be done after a factory reset.

Factory Reset

Writes the factory default settings in the non-volatile EEPROM and loads them then into the runtime memory.

Load Sequence

Loads the sequence stored in the non-volatile EEPROM into the runtime memory.

Save Sequence

Saves the sequence from the runtime memory in non-volatile EEPROM.

Clock Source

Selects the clock source if no trigger signal is supplied to the Clock-In socket. The setting does NOT affect the Start/Stop control.

Attention! Do not change these settings while the sequencer is running!

Start/Stop Source

Selects which source for start and stop commands is used.

Send Clock

Determines whether the SQ-4m sends clock signals when running with the internal clock.

Global Clock Ratio

Sets the relation of the internal 24bpq clock or MIDI/VMC-clock to the clock signal, which is sent to sequencer tracks

Transp. Center

Sets the note value, that corresponds to 'no transposition'

All product names and brand names beside "VMC-1", "SQ-4M" and "fanwander" belong to the corresponding owners. They are mentioned only for educational purposes.