Drums builds every hit from nothing, and says how

Drums is a sixteen-step drum machine whose eight voices are synthesised as they play. It has swing, tap tempo, eight pattern slots, a recorder, and a link that carries the entire pattern to whoever you send it to.

It is for beginners learning how a beat is put together, producers sketching an idea, and teachers — anyone who wants a drum machine in a tab with nothing to download and no account to make.

There are no samples. kit.js describes itself as having no sample, no fetch and no URL, and builds each voice from oscillators and noise shaped by envelopes, routed through voice buses to a master and out, with the recorder tapped off the master.¹ Each voice's recipe is written beside it: the kick is a sine swept from about 160 Hz down to 48 Hz in fifty milliseconds, with a noise transient; the clap is four bursts of noise near 1.1 kHz, about eleven milliseconds apart.²

Timing belongs to clock.js, a lookahead scheduler that writes each step into the audio clock at a sample-accurate time before it is due. Its pump runs twice — from the page and from a two-line Worker — because phones throttle idle page timers and leave a Worker's alone.³ Swing is defined exactly: every odd sixteenth is played late by the swing fraction of one step, with no running total, so the bar never stretches. Tap tempo averages the last eight taps and forgets any gap longer than two seconds.⁴

machine.js packs the whole machine — tempo, swing, length, kit, every cell and accent, each voice's level, tune and decay, and the mutes — into 62 bytes of base64url. The same encoding fills the slots and the share link, which carries it after #p= in the fragment, the part of an address browsers do not send to servers.⁵ The recorder, at 192 kbps, reads back the format the browser actually produced instead of assuming it.⁶

At 19:56 UTC on 27 September 2026 we sized the three scripts in a local copy of build 537: clock.js 7,005 bytes, kit.js 25,946 and machine.js 35,397. At 19:58:54 UTC the page itself returned HTTP 200 and 66,235 bytes.

That is about 68 KB of code and not a single audio file — every sound on the page comes from those bytes.

Drums plays a single pattern of up to sixteen steps. There is no song arrangement, no chaining of patterns, no per-step probability and no MIDI — and the page says so itself.⁹

It is not a sampler: eight synthesised voices are all you get, where Splice offers producer kits of real recordings. And latency is whatever your browser and device provide; on a phone, the page admits, you can feel it when tapping along.

Drums goes to the length of building every sound from arithmetic and publishing the recipe, of engineering its clock around the habits of phone browsers, of defining swing to the step, and of fitting a whole groove into a link the server never sees. It is a teaching instrument as much as a toy, and a good one.

When you need real samples, longer patterns or MIDI, Splice Beatmaker and Drumbit go further.

A beat machine that shows you how every sound is made, then lets you keep it.