How do analogue drum machines work?

Analogue-style drum synthesis is fairly straightforward once you get your head around the unique qualities of percussive sounds. Unlike melodic sounds such as basses and pads, percussive hits are largely about very fast transients, little to no sustain and, often, a large proportion of noise.

It’s worth knowing how some of the classic analogue drum machines make sounds – and how modern hardware units take that further.

Up until the 80s, all commercial drum machines were analogue. That means they generated their sounds using subtractive circuits equivalent to those found in regular synths. The key difference is that the circuits were simplified to meet the requirements of drum sounds, rather than basslines or melodies. Generally, the cheaper the drum machine, the more simplified the circuits; that’s one reason why so many old rhythm boxes sound weedy compared to more expensive analogue units like, say, the TR-808.

The typical approach was to build highly specialised circuits for each type of sound. To use the 808 as an example, there’s a dedicated bass drum circuit, a dedicated snare circuit and so on. Some of the circuits are shared between separate sounds, so you can have either maracas or a hand clap, say, but not both.

Some modern analogue drum machines follow the same approach, with dedicated circuits for each drum. You’ll find this on units such as the Arturia DrumBrute and Korg Volca Beats (the Volca also uses samples for tricky hi-hats, like the classic TR-909). The advantage is that it’s easier to program sounds, but the downside is fewer timbres. Just as an 808 kick always sounds like an 808, the DrumBrute and Volca don’t offer a huge amount of flexibility.

More complex modern drum machines take things a step further, offering a collection of far more versatile synth circuits. Take the DSI Tempest, which has six identical synth circuits or ‘voices’, each of which can be configured to create any sound you like. As a result, the choice of oscillators, envelopes and filters means you can synthesise all kinds of completely different kick, snares, hats or anything else. It’s more complex to program, but way more versatile.

Both approaches are found in analogue-style drum synth plugins. Emulations like D16 Drumazon use simple dedicated circuits for each sound, while all-rounders like Sonic Charge MicroTonic are more complex.