Modules for Voltage Modular

Big Purple Chord Sequencer

It's big. It's purple. It's a chord sequencer.
And better than that - it's got a wizard!


BPCS is an 8-step chord sequencer. Each step can be set to one of fourteen types of chord with a choice of three inversions. Each step also has independent gate length, duration and up to four repeats. Sequences can be transposed in semitones or shifted by whole octaves and there are a variety of selective randomizing options.

The BPCS also comes with a built-in wizard! I can't say whether our Wiz has a pointy hat but I can tell you that he has a big fat book of about 400 chord progressions and, as long as you don't upset him, with just one or two mouse clicks he will happily populate the chord section with a sequence of chords that he reckons makes musical sense.

Quick Start

The sequence runs from top to bottom. The chord names are shown in the middle of the screen. If the Chord Preview switch is on then the chords can be previewed by left-clicking on the chord names when play is stopped.

Connect the Chord and Gate outputs to a Poly synth.

Set the BPM and the number of steps.

For each step, set a chord with the four knobs to the left of the chord name, or by right-clicking on the chord name and choosing from the pop-up menu. That same pop-up menu has copy and paste at the top. You can copy a chord and paste it to one or more other steps.

Alternatively, click the "Wizard" button and choose a chord progression from the pop-up menu.

Press PLAY to hear one bar of each chord in turn. The red LED shows the current position

Each step has a gate length, a duration in beats and can be repeated up to four times. These are set by the three knobs to the right of the chord name. The total number of beats in the sequence is shown at the top.


Clk In

An (optional) external clock input. Every rising edge on this input advances the sequence by one beat. Connecting anything to this input disables the BPM knob and duplicates the incoming clock to the Clk Out socket.


A standard trigger input. A rising edge on this input resets the internal clock generator.


A standard trigger input. A rising edge on this input starts play.


A standard trigger input. A rising edge on this input stops play.


Clk Out

If no external clock is connected then this outputs the internal clock, set by the BPM knob. If an external clock is connected then this output is simply a copy of that clock

Root and Gate

A standard pair of mono outputs, sending out the root note of the chord. This output is not affected by the inversion setting - you still get the root note as set by the Root and Octave knobs.

Bass and Gate

A standard pair of mono outputs, sending out a note one octave below the lowest note in the chord. This output is affected by the inversion setting. As the inversion changes, so will this note.

Chord and Gate

The main output. A standard pair of poly outputs, sending out a chord of three, four or five notes. You'd typically drive a poly synth or an arpeggiator from here. Try incorporating a Poly Spreader to adjust the notes and maybe add a few more.


Stop and Play buttons

These stop and start the sequence.

BPM knob

This sets the tempo from 30 to 400 BPM. This knob is disabled if an external clock is connected.

Steps knob

This sets the number of active steps from 1 to 8.

Step buttons 1 to 8

These mute or unmute a particular step. A muted step is still "played through" but no notes are output.

Root and Oct knobs

These combine to make the root note for each step.

Type knobs

These set the chord type for each step. 14 types of chord: maj, min, dim, sus2, sus4, aug, 6, 7, maj7, min7, dim7, maj9, min9 and dim9.

Inv knobs

These set the inversion for each step. 0 is the root position (non-inverted). 1 and 2 are the first and second inversion respectively. "Slash notation" is used for displaying the chord name, showing the base note after the main chord name. For example, the first inversion of C Major is shown as "Cmaj / E" because E is the bass note of that inversion.

Gate knobs

These set the gate length of each step. With an internal clock the length is set as a percentage of the tempo. With an external clock the gate length is set in milliseconds.

Dur knobs

These set the duration of each step in beats from 1 to 8. The default value is 4, equating to one bar of 4/4 time.

Repeat knobs

These allow you to repeat the chord up to 4 times before moving onto the next step. Each repeat has the duration and gate length that is set by those two knobs. As you increase the repeats you will see extra LEDs appear next to the knob. Note that you may not hear distinct repeats if you set a long gate time - all the repeats will merge into one longer chord.

The combination of duration and repeats mean that each step can last between 1 and 32 beats. The overall length of the sequence in beats is shown at the top of the module to save you a bit of adding up!

Random Steps switch

Much as I would like to tell you that this switch randomizes the members of a manufactured UK pop band from the late nineties it actually just makes the sequence play in a different order. Each time a step is completed play will jump to a random one, which could even the same one that just played.

Chord Preview switch

This switch allows you to preview chords by left-clicking on their name when play is stopped.

Sharp/Flat switch

This just changes the chord annotation between sharps and flats. It has no effect on the notes you hear. My classically trained wife made me add this switch!

Various buttons along the bottom of the module, beneath the knobs

The RND buttons randomize the 8 knobs above them - type, inversion or gate length. The left/right buttons increase or decrease the root note or octave for all 8 steps. Note that a root button will affect the octave setting when it "wraps around" at the ends. This makes more sense musically - you can effectively transpose the whole sequence up or down a semitone at a time.

The "Shuffle Rhythm" button is a little different and has nothing to do with blues bands. Pressing this button randomly re-orders the rhythm part of the sequence, keeping duration and repeat knobs together but moving them to a different step so the total number of beats is unchanged. This makes more sense than just randomizing the knobs.

That Wizard button and its little helpers

The BPCS has a repertoire of around 400 chord progressions, all carefully guarded by an imaginary wizard, who may or may not be called Eric. Press the big friendly "Wizard" button and choose a progression from the pop-up menu. The progressions are loosely grouped into genres but don't let that shackle you - there are no rules. I reckon the first half of the "Basic" category covers a large chunk of every pop song ever written - just shift the root note up or down to suit. The helper buttons underneath the Wizard button let you cycle forwards and backwards through all the progressions or you can select a random one.

The Wizard only affects the chord selections and sets the number of steps to match the progression. Gate, duration and repeats are all unaffected.