reverb for synths and drum machines
electronic sounds are born dry, with no room baked in, and they punish reverbs designed for mic-recorded instruments. why synths and drum machines need different reverb, and what to actually reach for.
the sound with no room
you write a patch you love. a wide, moving pad, or a mean little drum-machine groove, and it sits in the mix sounding great and slightly pasted on, like a sticker on glass. so you reach for a reverb, load a nice hall, and it gets worse. now the pad is a smeared cloud and the drums have lost their snap, and you are further from where you wanted to be than when you started.
the reverb is not broken. it was built for a violin.
here is the thing most reverb tutorials skip: nearly every reverb preset you have ever loaded was voiced for sounds recorded with a microphone, and a synth is not one of those. a mic-recorded instrument comes to you with a room already attached. before you touch a single plugin, the recording carries early reflections, air, the natural decay of wherever it was played. a synth or a drum machine has none of that. it is a direct electronic signal, and it arrives in your session bone dry, with no space attached to it at all.
key takeaway
reverb on a mic-recorded instrument adds to a room that is already there. reverb on a synth builds the whole room from nothing. that is a bigger job, and it is why reverbs that flatter a vocal can wreck a pad.
that difference sounds academic until you hear it. because there is no existing space to blend into, everything the reverb does is exposed. it is like adding a shadow to a cartoon character versus adding one to a photograph: on the photo the shadow just deepens what is there, but on the drawing it has to invent the light source, the floor, and the angle all at once, and if any of it is wrong the whole thing looks fake. a reverb on a synth is inventing the light source. that is why the choice of reverb, and how you set it, matters more here than almost anywhere else in the mix.
the sustained-note problem
synths hold notes. that one fact causes half the trouble.
the trick that makes a good algorithmic reverb sound smooth instead of metallic is modulation: the reverb slowly wobbles the length of its internal delay lines so that no single frequency can ring out and turn the tail into a pitched pipe. on a plucked string or a snare, a tail that lasts a second or two, you never notice the wobble. on a synth pad that holds a chord for eight bars, you notice everything. the same modulation that saves a drum hit smears a sustained note into a faint, seasick detune, because the reverb is quite literally pitch-shifting its own tail up and down, and a held tone gives your ear all the time in the world to hear it.
why held notes expose the tail
de-metallising a reverb is a balancing act. static delay lines ring; the standard cure is to modulate them, but modulation moves pitch, and sustained harmonic material makes that pitch movement audible as chorusing or detune. the modern way out is to decorrelate the tail without moving pitch at all: research on time-varying feedback delay networks showed you can slowly vary the reverb’s internal feedback matrix over time to smear the resonances and kill the ring, while leaving the delay lengths (and therefore the pitch) fixed.[^1] that is exactly the kind of reverb a synth wants, one that stays smooth on an eight-bar chord without wobbling it. it is worth knowing the distinction, because if a reverb detunes your pads, no amount of preset-hunting fixes it; the pitch movement is baked into how that reverb hides its own resonances.
so the first thing to listen for on a synth reverb is not the size or the tone. it is whether a held chord stays in tune as the tail blooms. many reverbs fail that test quietly, and it is one of the biggest tells between a reverb that flatters electronic music and one that fights it.
the drum-machine problem is the opposite
where pads suffer from too much movement, drum machines suffer from not enough density. a drum machine fires fast, hard, repetitive transients, and a reverb answers each one by scattering it into a cloud of reflections. the question is how quickly that cloud fills in.
in a real room, reflections pile up fast: within a fraction of a second, thousands of them arrive per second and the ear hears a smooth wash. a cheap or thin reverb builds that density too slowly, so early in the tail you get a handful of discrete, sparse echoes instead of a smooth wash, and on a busy drum pattern those sparse early reflections sound grainy and fluttery, like the tail is made of gravel. schroeder identified this echo-density problem at the very beginning of artificial reverberation, and it has been a design target ever since.[^2] for drums, you want a reverb that reaches high echo density quickly, so every hit dissolves cleanly instead of rattling.
note
a fast, reliable drum-machine reverb recipe: high-pass the reverb send around 200-300 Hz so the wash never muddies the kick or 808. add 20-40 ms of pre-delay so the transient stays dry and punchy and the tail blooms behind it, not on top of it. start with a decay shorter than feels right, then lengthen it until the tail begins to blur the groove, and back off from there. and use a dense reverb, one that fills in fast, so the space between hits is smooth rather than gravelly.
the tail does not have to obey physics
there is one more freedom electronic music has that acoustic music does not, and it is the fun one.
in a real room, high frequencies die first. air itself absorbs high frequencies far more than low ones, and that absorption climbs steeply with frequency, so the top of a reverb tail always fades faster than the bottom.[^3] soft furnishings and surfaces pull the highs down further still. this is why a natural-sounding hall gets darker as it decays, and reverbs built to imitate rooms bake that darkening in. it is correct, and for a mic-recorded source it is what you want.
but a synth does not have to live in a real room. this is where electronic music gets to break the rules a physical space cannot. you can keep the highs alive so the tail shimmers instead of fading to mud. you can make the decay brighter over time, which no room on earth does. you can let low frequencies bloom longer than highs, or the reverse, or push the decay time in one part of the spectrum while another dies fast. once you stop trying to imitate a room, the tail becomes an instrument you shape rather than a physical process you accept.
that freedom is the whole reason i built OPEN the way i did. it is an algorithmic reverb aimed squarely at synthesis and drum machines rather than another plate emulation, with per-band control over how the tail decays, so a busy chord can clear quickly while a held note blooms, and highs can be kept or thrown away on purpose. it is in beta now; tick “i want to beta test future plugins” on the signup at /#signup to get in.
the short version
for a synth or a drum machine, forget the room presets and listen for four things: does a held chord stay in tune as the tail blooms (modulation), does the space fill in smoothly on fast hits (density), can you keep the transient dry and punchy while the tail sits behind it (pre-delay and high-passing), and can you shape the tone of the tail toward what the track wants rather than toward realism. get those right and a synth stops sounding pasted on and starts sounding placed.
frequently asked questions
frequently asked questions
what kind of reverb works best on synths?
an algorithmic reverb usually beats a convolution reverb on synths. a synth has no real room baked into it, so you are inventing a space from scratch rather than matching an existing one, and algorithmic reverbs are built for exactly that: they let you dial decay, size, and tone into whatever serves the track, including sizes and shapes no real room could have. convolution shines when you want a believable, specific real space, which a synth part rarely needs.
why do synths need different reverb than real instruments?
a mic-recorded instrument arrives with a room already attached: early reflections, air, the natural decay of the space it was played in. a synth or drum machine is a direct electronic signal with none of that, so it lands in the mix perfectly dry and slightly unreal. reverb on a synth is not adding to an existing sense of space, it is building the entire sense of space, which means it has to do more work and is more exposed when it does the work badly.
should I use algorithmic or convolution reverb on synths?
algorithmic, most of the time. synths do not need the realism of a captured room, and they often want spaces that could not exist physically, huge blooming tails, decay that gets brighter instead of darker, reverse swells. an algorithmic reverb gives you those; a convolution reverb ties you to whatever real room was sampled. reach for convolution on a synth only when you specifically want it to sound like it is in a real, identifiable place.
how do I stop reverb making my synth sound muddy or detuned?
two moves. for mud, high-pass the reverb send and shorten or damp the low end of the tail so the wash is not stacking bass under a sustained patch. for the shimmery detuned wobble on held notes, the culprit is the reverb modulating its own delay lines; either reduce the modulation depth if the plugin lets you, or use a reverb whose de-metallising trick does not rely on pitch-shifting the tail. sustained synth chords expose reverb modulation far more than percussive sources do.
what reverb settings work for drum machines and 808s?
keep it dense and controlled. drum-machine hits are fast and repetitive, so you want a reverb that reaches high echo density quickly, otherwise the tail sounds grainy and fluttery between hits. use pre-delay to keep the transient dry and punchy while the tail blooms behind it, high-pass the send so the reverb does not swamp the low end of a kick or 808, and keep decay shorter than your feel wants at first, then lengthen it until it starts to blur the groove and back off.
references
a note from the developer
i spent this spring building a reverb and, for a long stretch, testing it on exactly the wrong material. i kept feeding it drum hits and plucks, because those are what reverb demos always use, and it sounded great. then i put a sustained pad through it and heard the tail wobble, a seasick little detune on a held chord that never showed up on a snare. i had been auditioning the one case that hides the problem.
that is the trap with synth reverb in one sentence: the sounds that make a reverb look good in a demo are the opposite of the sounds that expose whether it is actually good for electronic music. a snare forgives everything. an eight-bar chord forgives nothing. so if you are judging a reverb for your synths, judge it on a long held note, not a drum loop, and you will find the truth in about four seconds.
if you make something with it, or you have a pad that will not stay in tune through a reverb, send it over. jonas@kernaudio.io. i read every email.