Guide 5 of 9 · Every Try it box opens the synth with its steps pinned on the rack

Rhythm: clocks, gates & sequencers

Until now, every note needed a finger on a key. But a modular synth can play itself, and keep perfect time doing it. All of it comes down to one humble signal: a steady stream of pulses.

The clock: a heartbeat on a cable

A Clock sends out pulses at a steady tempo, set by BPM (beats per minute). Its outputs are ordinary gates, jumping from 0 to 1 and back: one fires every sixteenth note (1/16), one every eighth (1/8), one every beat (1/4) and one every BAR.

That's it. There's nothing special about a clock signal, which is the whole point: anything that listens for a gate can be played by a clock. What modules listen for is the rising edge, the moment the signal jumps from low to high. That moment means "now".

Swing delays every other sixteenth a little, turning stiff, robotic timing into a shuffle.

The sequencer: a melody that plays itself

A Step Sequencer holds a row of notes. Every pulse into its CLK moves it one step along, and it sends out two signals for the current step: V/OCT (which note) and GATE (play it or not). If those sound familiar, it's because they're exactly what a keyboard sends. A sequencer is just a pair of hands that never get tired.

Drums: gates you can hear

The Drum Trio has three voices (kick, snare and hat), and each one plays on every rising edge at its input. Any gate works: a clock, a sequencer, even an LFO set to a square wave.

The simplest beat is the Clock's 1/4 straight into the kick: four on the floor. For the rest, meet the Euclid sequencer.

Euclidean rhythms: two numbers, endless grooves

Euclid takes two numbers, Steps and Hits, and spreads the hits as evenly as possible over the steps. That one rule turns out a surprising amount of the world's music: 3 hits in 8 steps is the tresillo heard all over Latin and pop music; 5 in 8 is the Cuban cinquillo. Rot rotates the pattern so it starts in a different place.

Try itA beat from two numbers

A Clock, two Euclids and a Drum Trio, with no cables. Build the beat one drum at a time:

Patch the Drum Trio's MIX into the Output's MONO. Silence: nothing is hitting the drums yet.
Patch the Clock's 1/4 into the Drum Trio's KICK: four on the floor.
Patch the Clock's 1/16 into the CLK of both Euclids, so they step along in sixteenths.
The first Euclid is 2 hits in 16 steps, rotated 4. Patch its HIT into the Drum Trio's SNR: that puts the snare on beats 2 and 4.
The second is 7 hits in 16: lopsided and groovy. Patch its HIT into the HAT.

Then play with it:

Change the hats' Hits and Rot while it plays.
Turn the Clock's BPM up and down. The pattern stays exactly the same, just faster or slower, because every drum is counting the same clock.

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The drum grid

If you'd rather place every hit yourself, the Drum Seq is a classic drum machine grid: four lanes, sixteen steps, click to add a hit. With the Clock's 1/16 stepping it, sixteen steps is one bar.

One clock, many rhythms

Because a clock is just a signal, you can do maths with it.

A Clock Divider fires on every 2nd, 3rd, 4th or 8th pulse. Send ÷4 to the kick and ÷3 to the snare and you get 3 against 4: two patterns that only line up every 12 ticks. That's a polyrhythm, and it sounds far more complicated than it is to patch.

Logic combines two gates into a new one. AND fires only when both are high, OR when either is, XOR when one is but not both.

Try itPolyrhythms from one pulse

A Clock, a Clock Divider, a Logic module and a Drum Trio, with no cables. Build the beat one drum at a time:

Patch the Drum Trio's MIX into the Output's MONO, and the Clock's 1/16 into the Divider's CLK. Silence: nothing is hitting the drums yet.
Patch the Divider's ÷4 into the Drum Trio's KICK. Four sixteenths make a beat, so that's a kick on every beat.
Patch the Divider's ÷3 into the SNR: a snare on every third sixteenth. Listen to it drift against the kick. The two only land together every 12 ticks: that's 3 against 4.
Now mark where they meet. Patch ÷4 into the Logic's A and ÷3 into its B (outputs can feed as many inputs as you like), then the Logic's AND into the HAT. A hat plays only when kick and snare land together, so you can hear each 12-tick cycle start.
Move the hat cable from AND to XOR. Now the hat plays whenever exactly one of them fires, filling the gaps between kick and snare.

⏻ Build lesson 28 in KablesThe modules are waiting, unpatched. These steps come with you.

One more to try: the Divider's A and B outputs are a coin toss, each tick going randomly to one of them. Patch B into the SNR as well for surprise ghost notes.

Changing things on the bar

A Switch passes one of its inputs through and moves to the next on every pulse into STEP. Feed it two sequencers' melodies and step it with the Clock's BAR, and the tune changes every bar, all from one clock.

Ratchets and rolls

Sometimes one hit isn't enough. Burst turns a single trigger into a quick roll. With the clock patched into its CLK, the whole roll fits exactly inside one step, so it always lands in time. Drummers call that a ratchet.

Why everything shares one clock

Every pattern in these patches comes from a single Clock. That's why they never drift apart: sequencers, drums, dividers and switches all move on the same pulse. Change the BPM and everything follows. It's the same in hardware modular, where a single clock module often drives a whole case.

What to remember

A clock is just a steady stream of gates. Modules act on the rising edge, the moment it goes high.
A sequencer sends V/OCT and GATE, just like a keyboard, one step per clock pulse.
Euclidean rhythms spread N hits over M steps, and many classic grooves fall out of that rule.
Dividing and combining one clock makes polyrhythms that always stay in time.
Odd lengths and chance keep repeating patterns from sounding repetitive.