Backbeat

A whole drum kit with no samples in it: a kick that drops in pitch, a snare with ghost notes between the backbeats, a hi-hat that opens and gets choked shut, a run down the toms every fourth bar, and a crash where the fill lands. Every drum is an oscillator or a noise source shaped by an envelope. It plays itself; press Play and let it run.

To learn how drums are made, build them like this. To make a beat quickly, use the Drum module, one per drum: the Drum Machine example plays a kit like this in 14 modules.

Load it: choose 📚 Examples → Backbeat in the toolbar and press ▶ Play. It needs no keyboard. The patch file is patches/backbeat.json.

Or play it here: press ▶ Play in the corner. The full app is a click away under Open in Soba. One lane per drum, from the top: kick, snare, hi-hats, toms, crash. The clock is at the top left. The Clock Divider that schedules the fill sits lower down in the same column. Kick and snare mix, compress and land on a drum bus at the top right. Below and to the right, the main Mixer brings the whole kit together, shares one small room among every drum, and feeds the output through a Tape.

What it teaches

• Drums from oscillators and noise. A kick is a sine that falls in pitch. A snare is a tone plus a burst of filtered noise. Hats and cymbals are noise with the low end removed.
• Accents and ghost notes. Each sequencer step has a velocity, and the envelopes turn velocity into loudness. The same snare plays a backbeat and a whisper.
• A sequencer's pitch as a switch. The hi-hat lane's pitch output is a flag that says whether the hat is open. That flag also chokes it.
• Phrases longer than a bar. A 16-step sequencer loops every bar. For a fill every fourth bar, a Clock Divider counts the sixteenths and opens a gate once every 64.
• One room for the whole kit. A drum-bus Mixer chains into the main one over a single cable, and each part sends its own amount to a single reverb, as on a mixing console.

The pattern

Sixteen steps a bar at 96 BPM. X is an accent, x a softer hit, g a ghost note, o an open hat, ~ a hat still ringing.

step     1 . . . 5 . . . 9 . . . 13. . .
kick     X . x . . . . . . x X . . . . .
snare    . . . . X . . g . . . . X . g g
hats     X x x x X x o ~ X x x x X x o ~
toms (every 4th bar)     G G D D A A E E
crash    on the downbeat after each fill

Modules

All drum envelopes have a 1 ms attack and 0% sustain. The sequencers' gates are a fixed 99 ms (Gate of 100 ms), so each envelope's Release matches its Decay: the sound falls at the same rate after the gate closes.

How it's built

The kick

[Kick Seq Gate] ──> [Kick Pitch Env Gate]  [Kick Level Env Gate]  [Oscillator Sync]
[Kick Pitch Env Out] ──> [Oscillator Exp FM]
[Oscillator Out] ──> [VCA In]
[Kick Level Env Out] ──> [VCA CV]

A kick drum's thump is a pitch falling fast. The pitch envelope, at 2.6 octaves of Exp FM, starts the sine at about 330 Hz and drops it to 55 Hz in about 45 ms. The ear hears the drop as the beater hitting the drum and the low sine as the body. The same gate patched into Sync restarts the sine at zero on every hit. Without it, each kick would start at a random point in the cycle and land slightly differently.

The snare

[Snare Seq Gate] ──> [Body Env Gate]  [Noise Env Gate]  [Oscillator Sync]
[Body Env Out] ──> [Oscillator Exp FM]  [VCA CV]
[Noise Env Out] ──> [Noise Level]
[Noise White] ──> [SVF Filter In]

A snare is two sounds. A triangle at 196 Hz, with a short dip in pitch, is the drum's shell. White noise above 1.8 kHz is the rattle of the wires under it. The noise lasts about twice as long as the tone, so each hit ends in a hiss.

Both envelopes have Vel at 85%, so velocity matters. The backbeats on 2 and 4 play at 122. The ghost notes at 26 to 40 come out about a third as loud. They sit under the groove and make it swing a little, the way a drummer's left hand does.

Hats that choke

[Hat Seq Gate] ──> [Closed Env Gate]  [Open Env Gate]
[Closed Env Out] ──> [Noise (closed) Level]
[Open Env Out] ──> [VCA (choke) In]
[Hat Seq Pitch] ──> [VCA (choke) CV]
[VCA (choke) Out] ──> [Noise (open) Level]

On a real hi-hat, the open sound rings until the drummer closes the pedal. Every hat step fires both envelopes. The open hat's long envelope only reaches its noise through a VCA, and the hat lane's Pitch output opens that VCA. Steps set to C4 send 0 V and keep it shut. Steps set to C5 send 1 V and open it.

So on steps 7 and 15, set to C5, the hat opens. Steps 8 and 16 are also set to C5 but their gates are off, so the hat keeps ringing. On steps 9 and 1 the pitch drops back to C4, and the VCA cuts the ringing off as the closed hat plays. That's the choke. To make the hat ring longer, set the next step to C5 too.

The fill and the crash

[Clock Gate] ──> [Clock Divider Clock]
[Clock Divider Gate] ──> [Tom Seq Run]  [Tom Seq Reset]  [Attenuverter In]
[Attenuverter Out] ──> [Mixer Level 1]  [Mixer Level 2]
[Tom Seq EOC] ──> [Crash Env Gate]

A 16-step sequencer can't wait three bars before it plays. The Clock Divider does the waiting. It counts the Clock's sixteenths, and 64 of them are four bars. On count 0, the downbeat of bar 1, its Gate opens: the tom sequencer resets to step 1 and starts running. The toms play their fill on steps 9 to 16, two hits on each drum from G down to E.

The Gate stays open for 17 clocks, Length 17: the fill bar and the downbeat after it. That one extra clock lets the tom sequencer take one more step and wrap round, and its EOC pulse strikes the crash on the next downbeat. Then the Gate closes and the toms wait for count 0 again. The same Gate, inverted by the Attenuverter, pulls both hat faders to zero, so the hats stop for the fill and come back with the crash.

Because the divider counts the Clock's own pulses, it can't drift from the beat, however long the patch plays, and it follows the Clock to any tempo. The fill also plays in the very first bar, so the patch opens with a count-in down the toms and lands on a crash.

Toms across the kit

[Tom Seq Pitch] ──> [Oscillator V/Oct]  [Mixer Pan 3]

One oscillator plays all four toms. The sequencer's Pitch picks the drum, with the toms tuned in fourths: G, D, A, E. The same pitch goes into the Mixer's Pan 3, so high toms sit right and low ones left. The fill sweeps across the stereo field, the way a real kit does from the audience.

Mixing

[Kick/Snare Mix Out] ──> [Compressor In]
[Compressor Out] ──> [Drum Bus Mixer Ch 1]
[Drum Bus Mixer Chain Out] ──> [Main Mixer Chain In]
[Main Mixer Send L/R] ──> [Reverb In L/R]
[Reverb Out L/R] ──> [Main Mixer Return L/R]
[Main Mixer Out L/R] ──> [Tape In L/R]
[Tape Out L/R] ──> [Audio Output Left/Right]

Kick and snare are added on a Mix and go through a compressor, which glues them together. The compressor's 8 ms attack lets each hit's crack through before it starts to work. Its output is the only channel of a small drum-bus Mixer, centred. A centred channel is 3 dB down on each side, so the bus's Master at +3 dB gives it back. The bus's Chain Out carries its mix and its send into the main Mixer's Chain In on one cable. Hats, toms and crash have the main Mixer's four channels, each panned to its place.

There is one room for the whole kit: a short reverb, 0.9 seconds long and fully wet. Every part decides how much of it to hear. On the main Mixer each channel sends 25%. The drum bus sends 15% of the compressed kick and snare, less than the rest, to keep the low end tight. Its send travels to the main Mixer on the chain, joins the main Mixer's own, and the reverb hears them all on the main Mixer's Send L and Send R.

The reverb comes back on the main Mixer's Return. That closes a loop, from the Mixer to the reverb and back, which the Return allows by hearing the reverb one audio block late, about 5 ms. The reverb's pre-delay is 2.5 ms, a little shorter than the room's natural 8 ms, to make up for it.

The hats, toms and crash have exactly the balance they had when the whole second Mixer ran through the reverb at 20%: faders at 0.8 of their old level keep the dry, and a 25% send after them keeps the wet.

The whole kit goes to tape on its way out. Wow, flutter, age and hiss are all at zero, which leaves only the saturation, at 10%. The first few milliseconds of a hit are far louder than the rest of it, and the tape rounds off their tops, as a machine does when a kit is recorded hot. That takes about 3 dB off the peaks and hardly touches anything quieter, so the kit comes up to the level of the other examples and its peaks still stay under the Output's limiter. The kick's level envelope rings for 700 ms for the same reason: a longer body adds loudness under the same peak. A compressor on the mix can't do this job. One slow enough to let the crack through turns down the body of each hit and leaves the peak where it was.

Variations

Tighter or looser kick. Shorten the kick pitch envelope's Dec to 25 ms for a clicky dance kick, or lengthen it to 90 ms for a boomy one. Raise the level envelope's Dec to 900 ms for an 808-style tail.

Hotter tape. Raise the Tape's Sat to 30%. The level hardly moves, because the tape makes up the drive it adds, but the kit sounds recorded harder: the hits rounder and denser, and the hats sinking a little under each kick.

More snare. Turn the snare filter's Cutoff down to 900 Hz for a fatter, rougher snare, or set it to BandPass at 4 kHz for a thin, crisp one.

Busier hats. Set another step to C5 to open the hat there. Set the step after it to C5 as well to let it ring.

Half-time. Turn off the snare's steps 5 and 13 and turn on step 9. With one backbeat a bar instead of two, the same tempo feels half as fast and twice as heavy.

A different fill. The toms play steps 9 to 16. Turn on steps 1 to 8 for a whole-bar fill, or change the pitches for a different run.

More room, or less. The drum bus's Send 1 sets how far back the kick and snare sit: 40% pushes them to the back of the room, 0% puts them right in your ear, dry and tight. Turn the main Mixer's Send 1 and Send 2 down for dry, close hats, or Send 4 up for a crash that hangs in the air.

Swing it. Turn the Clock's Swing to about 58%. Every off-beat sixteenth lands a little late, while the downbeats and the backbeat stay on the grid. The pattern stops sounding programmed and starts to sit in a pocket. At 66% it becomes a full triplet shuffle.

Faster or slower. Turn the Clock's BPM. The fill stays on every fourth bar at any tempo, because the divider counts the Clock's own sixteenths.

A longer phrase. Set the Clock Divider's Div to 128 for a fill every eighth bar. Set Offset to 48, or 112 with Div 128, and the fill moves to the last bar of the phrase, with the crash on the first bar of the next one, the way drummers usually phrase it.

Related

• Drum Machine – a kit like this one in 14 modules, with a Drum module for each drum
• Roll Call – eight drums on one Trigger Sequencer, whose Chain plays the fill every fourth bar with no phrase clock
• Rhythmic Sequence – the noise hi-hat this kit's hats grew from
• Afterglow – another patch where one sequencer's end of cycle drives another
• Step Sequencer – pitch, gate, velocity, and what the outputs carry
• Noise – the source of every snare, hat and cymbal here