Drum Machine

A drum machine in 14 modules: one Clock, five sequencer lanes, and a Drum voice on each lane. It plays a swung groove with a kick, a snare with ghost notes, closed and open hats, and three tuned toms. Backbeat builds a kit like this from oscillators, noise and envelopes, in 37 modules and 67 cables. Here each drum is one module, and the whole patch has 31 cables. It plays itself; press Play and let it run.

Load it: choose 📚 Examples → Drum Machine in the toolbar and press ▶ Play. It needs no keyboard. The patch file is patches/drum-machine.json.

Or play it here: press ▶ Play in the corner. The full app is a click away under Open in Soba. Time on the left, then one lane per drum from the top: kick, snare, closed hat, open hat, toms. Each sequencer plays the Drum beside it. The Mixer, a touch of room and the output sit at the right.

What it teaches

• One module per drum. A Drum's Type makes it a kick, a snare or a hat, and its five knobs mean what they would on that drum.
• Velocity as accent. Each lane's Velocity goes to its Drum's Accent. A soft hit is quieter and darker, so a ghost note sounds different from a backbeat, not just quieter.
• A choke group. The closed hat's trigger also chokes the open hat, as the pedal does on a real kit.
• Tuned percussion. The tom lane's Pitch drives its Drum's Tune, so the sequencer plays the toms like a bassline.
• Swing. The Clock's Swing at 56% pushes every second sixteenth a little late, which puts the groove in a pocket.

The pattern

Sixteen steps a bar at 100 BPM. X is an accent, x a softer hit, g a ghost note, o a short open hat, O a long one, ~ a hat still ringing. The tom notes are on the steps they play.

step     1 . . . 5 . . . 9 . . . 13. . .
kick     X . . . . . . x . . X . . . . .
snare    . . . . X . g . . g . . X . g .
hats     X x X x X x o x X x X x X x O ~
toms     . . . . . G . . . . . . . D . A#

Modules

How it's built

Five lanes

[Clock Gate]  ──> [every Sequencer Clock]
[Clock Reset] ──> [every Sequencer Reset]
[Sequencer Gate]     ──> [its Drum Trig]
[Sequencer Velocity] ──> [its Drum Accent]

The Clock ticks sixteenths into all five sequencers, and its Reset starts them together on step 1 whenever it starts. Each sequencer is one lane of the kit: a step that's on strikes the Drum beside it, at the step's velocity.

A drum only cares when its trigger rises, so the length of the gate doesn't matter. Each hit lasts as long as its Drum's Decay.

The kick and snare

The kick hits on 1, the last sixteenth of beat 2 and the and of 3. Each hit drops two and a half octaves to 45 Hz, most of the way in the first 20 ms. Snap at 55% sets how far it falls and how hard the beater clicks. Tone at 35% rounds the sine off a little, so the kick carries on small speakers. Decay at 80% lets the body ring for over a second, so the kick on the and of 3 lands while the one before it is still sounding, 20 dB down.

That long body is what lets the kit play as loud as the other examples. The kick is nearly all of the kit's loudness, and its loudest instant is the first few milliseconds of the drop. A longer body adds loudness without raising that peak. With the kick at 45%, the kit had to play 3 dB quieter to keep its peaks under the Output's limiter. A compressor on the mix doesn't help: one slow enough to let the crack through turns the body down and leaves the peak where it was.

The snare's backbeats on 2 and 4 play at full velocity. Its three ghost notes play at 34 to 46 out of 127, about a third. At that accent the Drum plays them about 10 dB down and darker, with less of the wires, so they sit under the groove like a drummer's left hand.

The hats, and the choke

[Closed Seq Gate] ──> [Closed Hat Trig]
                 └──> [Open Hat Choke]
[Open Seq Gate]   ──> [Open Hat Trig]

The closed hats play every sixteenth except steps 7, 15 and 16, with the eighths louder than the sixteenths between them. The open hat plays on 7 and 15. Its decay is long, but it never rings out. On step 7 the closed hat on 8 cuts it off after a sixteenth, a quick tsk. On step 15 nothing closes it until the next bar's first step, so it breathes for two sixteenths. That's what a drummer's foot does.

Both hats are panned a little right, where they sit on a kit seen from the audience.

The toms

[Tom Seq Pitch]    ──> [Tom Tune]
[Tom Seq Gate]     ──> [Tom Trig]
[Tom Seq Velocity] ──> [Tom Accent]

The tom lane's notes become its pitch: middle C plays the tom at the Tune knob's 110 Hz, and each semitone away moves it one semitone. G3 on step 6 is a low answer to the kick. D4 and A#3 at the end of the bar lead back into the downbeat.

The mix

Snare, hats and toms take the Mixer's four channels. The kick comes in on Return L alone, which puts it dead centre at the Return level. The mix goes through a small room, mostly dry at 14% wet, with 8 ms of pre-delay so each hit's crack stays clear of its reverb.

Variations

A clap. Set the snare's Type to Clap. Its four bursts land on the backbeats, and the ghost notes become soft claps. For both, add a second Drum set to Clap, patch the snare lane's Gate to it too, and mix it in.

The 808 cowbell. Set the toms' Type to Cowbell. The tom lane's three notes become a cowbell figure.

An 808 boom. Set the kick's Decay to 95%, Tone to 10% and Snap to 30%. The kick becomes a long, pure sub that rings into the next hit. Tune it to the key of whatever plays over it.

Let the hat breathe. Turn off the closed hat's step 8. The open hat on 7 now rings until step 9.

A cymbal. Set the open hat's Type to Cymbal and Decay to 30%. The closed hats still choke it, so it plays as a short splash.

Straight or shuffled. Turn the Clock's Swing to 50% for a straight, programmed feel. At 62% the groove leans back, and at 66% it becomes a full shuffle.

Make it yours. Click a step on any lane's grid to turn its gate on or off, and the Drum beside it plays the new pattern. Steps you add play at velocity 100. Velocities can't be edited on the node yet, so ghost notes need the patch file.

Related

• Drum – each type, what its knobs do, and how a choke works
• Roll Call – eight drums on one Trigger Sequencer, with rolls and a fill every four bars
• Backbeat – the same kind of kit built from oscillators, noise and envelopes, and a fill every fourth bar
• Step Sequencer – pitch, gate, velocity, and what the outputs carry
• Clock – tempo and swing