If you want a sound to feel bigger but stay at the front of the mix with its words or hits clear, use a delay. If you want it to sound like it was played in a room, a hall or on a stage, use a reverb.
On vocals the two usually work together: a short reverb for the space and a quieter synced delay for depth.
At a glance
| Property | Delay | Reverb |
|---|---|---|
| What you hear | Separate repeats | One continuous wash |
| Echoes in the first second | Usually 1 to 8 | Thousands |
| Spacing | Even, set by the delay time | Uneven, and denser as it goes |
| Main controls | Time, feedback, mix | Decay, pre-delay, size, mix |
| Gaps between sounds | Stay mostly dry | Fill up |
| Where it puts the sound | Up front, with depth behind | Further back, in a space |
| Rhythm | Adds its own, often synced to the tempo | None |
| Typical uses | Vocal throws, guitar and synth leads, dub | Putting a mix in one space, drums, pads, ballads |
Is reverb just lots of delays?
Both effects play a sound back again, later and quieter, on top of the original. The difference is how many copies there are and how they're spaced.
A delay makes a handful of copies at a fixed time apart. With the delay time at 500 ms and the feedback at 45%, you get one repeat every half second, each about 7 dB quieter than the one before, and nine of them before they've fallen 60 dB. You can count them, and the lab does: in step 2 the first stat under Right now reads 2, the number of echoes in the first second.
A reverb copies what a real space does. When you clap in a hall, the sound bounces off the walls, the floor, the ceiling and every surface in between, and each bounce reaches your ears as its own echo. The number of reflections arriving each second grows with the square of the time since the clap, so within a fraction of a second there are thousands of them, overlapping. Switch the lab to Reverb and the echo count jumps into the tens of thousands, because the reverb's impulse response has no silent gaps left in it.
Reverb plug-ins are often built from delays too. An algorithmic reverb, the kind that works out its reflections in code, is a network of short delay lines feeding back into each other. Manfred Schroeder's 1962 design used four delays with feedback running side by side, followed by two allpass filters to scatter their echoes, and the delay times were chosen so that none of the repeats line up.
Reading the decay taps screen
The lower screen in the lab shows what the effect does to a single click, measured in half-millisecond slices. Height is level, down to 60 dB under the loudest moment, and time runs left to right from the click at the left edge.
A delay draws separate lines with nothing between them, one per repeat. A reverb draws a solid shape, because no slice anywhere in its response is silent. The pale shape behind the coloured one is the other effect at its current settings, so the comparison is always on screen. Hover over any line to read which repeat it is and how far down it sits.
The lab sends that click through the same convolution as the audio you hear, so the picture and the sound come from the same samples.
Why can't a fast delay sound like a reverb?
It seems like it should work: shorten the delay time until the repeats are too close to hear, turn up the feedback, and you'd have a wash. Step 4 of the lab tries it with repeats every 15 ms and 70% feedback, and the result rings like a metal tube.
Evenly spaced echoes boost some frequencies and cancel others. Repeats 15 ms apart arrive 1000 ÷ 15 ≈ 67 times a second, so every frequency that's a multiple of about 67 Hz lines up with itself on each pass and gets louder, and the sound takes on that pitch. That pattern of boosts and cuts is a comb filter, the same thing a flanger sweeps up and down.
Real rooms don't ring like that because their reflections arrive at uneven times, and a good reverb copies the unevenness on purpose. A spring reverb, which sends the sound down a coiled spring, is the exception you can hear. The sound reflects back and forth between the ends of the spring at regular intervals, and high and low frequencies travel along it at different speeds, which together give it its metallic boing.
Delay keeps a sound close, reverb pushes it back
Your ears judge distance partly by how much reflected sound there is compared with direct sound. Close to a singer, you hear mostly their voice; at the back of a hall, you hear mostly the room. Reverb adds that reflected sound everywhere, so the more you use, the further away the sound seems.
A delay adds space without moving the sound back. The repeats fall in the gaps, behind the sound, and the dry part stays clean, so a vocal with a delay on it still sounds as if it's right in front of you. It's a common way to keep a pop or rap vocal dry and close without it sounding flat: a delay does most of the work, with a little short reverb at most.
Rhythm is the other difference. Every delay repeat is a copy of the original, notes and all, so a delay adds a rhythm to the part. Synced to the tempo, that becomes part of the groove. At 120 BPM a 1/4 note is 60,000 ÷ 120 = 500 ms, and a dotted 1/8 is three quarters of that, 375 ms. A reverb never adds rhythm; it only makes each sound last longer.
Pre-delay: a delay inside the reverb
Pre-delay is the gap between the dry sound and the start of the reverb, and it's a delay in its own right. It has one repeat and no feedback. In step 5 the lab adds 60 ms of it, and the solid shape on the decay taps screen slides 60 ms to the right, away from the click.
It does in miniature what a delay does in a mix. The first 20 to 80 ms of each word or hit plays on its own before the reverb arrives, so consonants and drum attacks stay clear even though the space sounds big. Push past about 100 ms and you'll start to hear the reverb arrive as its own event, a little like a single echo with a wash behind it. The pre-delay lesson covers how to set it.
When to use reverb and when to use delay
| Job | Delay | Reverb |
|---|---|---|
| Lead vocal in a busy mix | Good, synced and filtered | Short and quiet |
| Ballad or sparse vocal | As an extra | Good, longer decay |
| Echo on the last word of a line | Good, as a throw | Works, with a long tail |
| Making a dry recording sound live | No | Good, a room |
| Snare or drum bus | Rhythmic effect only | Good, short room or plate |
| Lead synth or guitar solo | Good, synced | Good, plate or hall |
| Pads and ambient parts | Long, with high feedback | Good, long hall |
| Fast rap or busy drums | Short slapback or none | Very short, or it smears |
Pick delay when the gaps matter. Fast vocals, busy drum patterns and dense mixes have little room between their notes, and a reverb fills that room with sound. A delay leaves most of the gaps dry and drops copies into only some of them, so the part stays easy to follow.
Pick reverb when the sound needs a place. A vocal recorded close to the microphone in a treated booth sounds unnaturally dry on its own, and a short room or plate makes it sound like it was sung somewhere. Use reverb, too, when several parts need to sound as if they were played in one shared space; a handful of evenly spaced repeats doesn't describe a room, so a delay can't do that.
A send is the usual way to use either, with the effect at 100% wet on its own return channel and each track sending as much as it needs. The insert vs send lesson explains the setup.
How to use reverb and delay together on a vocal
Using both is normal, and it often sounds better than a lot of either, because each can then be quieter than it would need to be alone. This is a starting point for a lead vocal at any tempo.
- Set up two sendsPut a reverb on one return channel and a delay on another, both at 100% wet, and send the vocal to each.
- Start with a short reverbA plate or small hall with 1 to 1.8 seconds of decay and 20 to 40 ms of pre-delay. Bring the send up until you'd miss it if it went, then pull it back a decibel or two.
- Sync the delaySet it to a 1/4 or dotted 1/8 note with 20 to 35% feedback, so you hear two or three repeats before they fade.
- Filter the delayCut the lows below about 300 Hz and the highs above about 4 kHz on the delay return, so the repeats sit behind the voice and don't fight the consonants.
- Duck it if the words blurA ducked delay turns the repeats down while the singer is singing and lets them through in the gaps.
- Check them togetherPlay the full mix and mute each send in turn. If muting one makes no difference, turn it down or remove it.
If the repeats sound too clean against the reverb, send a little of the delay return into the reverb as well. Each repeat then gets its own small tail, which blends the two.
Common mistakes
Using reverb to make a lead vocal bigger
More reverb makes a vocal sound further away, which is usually the opposite of what you want for the lead. If a dry vocal feels small, try a quiet synced delay before adding reverb, and keep the reverb short.
Delay times that ignore the tempo
A delay at a random time adds a second rhythm that fights the song. Use your delay's sync option or work it out: 60,000 ÷ BPM gives a 1/4 note in milliseconds. Free times are fine for slapback, under about 150 ms, where the single repeat is too quick to sound like a rhythm.
Leaving the low end in both
Bass under 200 Hz or so in a reverb or delay return rarely adds space you can hear, but it does fill the bottom of the mix with smeared low notes. Put a high-pass filter on each return.
Judging the effect on its own
A long reverb or a busy delay can sound great with the track soloed and drown it in the full mix. Set the level of each send with everything playing.
Training your ears to tell them apart
The quiz under the lab plays the loop through a delay, a reverb or both, at low mix levels and the same loudness, with the screens covered. Listen to the gaps between phrases. Separate copies of the last word mean a delay and a smooth fade means a reverb; copies with a fade under them are both.
Questions people ask
Is reverb just a lot of delays?
In a way, yes. A reverb is thousands of reflections, and each reflection is a delayed, quieter copy of the sound. Algorithmic reverbs are built that way, from networks of short delay lines feeding into each other. It sounds like a space because the echoes come so close together, and so unevenly spaced, that you can't pick any of them out.
Should I use reverb or delay on vocals?
Plenty of pop and hip-hop vocals use both. If you only use one, a synced delay keeps the vocal closer and the words clearer, while a reverb sounds more natural and puts the singer in a room. Try the delay first on a busy track and the reverb first on a sparse one.
Does delay or reverb go first?
On separate sends the order doesn't matter, because each one gets its own copy of the dry sound. If you chain them on one track, delay then reverb is the usual choice, since the reverb then softens every repeat as well as the original.
Why does my reverb make the mix muddy?
A reverb fills every gap with sound, and a long one keeps the low end ringing. Cut the lows from the reverb return with a high-pass filter somewhere between 200 and 500 Hz, shorten the decay, or swap it for a delay, which leaves the gaps between its repeats dry.
What is the difference between echo and delay?
Echo is what you hear: a repeat far enough behind the original to sound separate, usually more than about 30 to 50 ms. Delay is the effect that makes it. Plug-in names use the two words for the same thing.
Can a delay sound like a reverb?
Partly. Several delays at uneven times, or a delay with a diffusion control, blur the repeats into something close to a reverb. A single delay with feedback never gets there, because its echoes are evenly spaced, and at short times they ring at a pitch.