What is reverb?

By Dan Murtagh · Updated

Short answer: reverb is the sound of a space: reflections off the walls, floor and ceiling that keep arriving after the direct sound and blur into a tail that dies away. In a mix it tells you how big the room is and how far away a part sits. To hear it, listen in the gaps: when a word or a hit stops, the tail hangs on. The two controls that matter most are how much (the send) and how long (the decay).

The lead vocal from an indie rock track, with the room Match the Space uses added under it (25 ms of pre-delay), the same room at different lengths. Short decay is 0.6 s and Long decay 2.4 s, both with the room 6 dB under the voice. Pushed back has a 1.4 s decay with the room as loud as the voice. Both sides play at the same loudness, so the reverb can’t win by adding level. Start with the vocal on its own, then hear it with the band.

What reverb is

In a room, you hear a sound first straight from the source. Then come the early reflections, the first bounces off nearby surfaces, which tell you the size and shape of the space. After that the reflections pile up so densely they become one smooth tail.

Decay time is how long that tail takes to fall away, measured as the time to drop 60 dB. A small room dies away in well under a second. A big hall can hang on for two seconds or more.

How to hear reverb

  • Listen in the gaps: the end of a word, or the space after a snare hit. That’s where the tail shows.
  • Flip it off: the part suddenly sounding dry and close tells you how much there was.
  • Check it with the band: reverb that’s obvious solo can vanish in the mix, and a tail that sounds right solo can cloud it.

In the demo, start with Long decay on the vocal alone, then switch to Short decay: the amount is the same, only the length changes. Then try Pushed back with the band.

The controls

  • Send, or wet level: how much room surrounds the part. More puts it further back.
  • Decay: how long the tail hangs on. Long tails blur fast parts.
  • Pre-delay: a short gap before the reverb starts, so the dry sound stays up front.

What reverb does in a mix

It places parts front to back. A part further away is quieter against the band, has more room around it, and loses some top end. A shared room also helps parts sound like they were played together.

How much is a style choice. Some music is wet, epic and lush; some keeps the vocal dry and right up front. Compare with a reference in the same style, and judge it with the band playing, not solo. Reverb is not the same as echo: a delay repeats the sound in distinct copies, where reverb blurs into one tail.

Questions

What does reverb do to a sound?

It adds the reflections of a space after the sound, so it seems to sit in a room. More reverb makes a part sound further away; a longer decay makes the room sound bigger.

What is a reverb send?

A send copies some of a track’s signal to a bus with the reverb on it, fully wet. You set how much of each part goes to the room, and several parts can share one space.

What is reverb decay time?

How long the tail takes to fade, measured as the time to fall 60 dB. Short decays suggest small rooms, long ones halls.

How much reverb should I use?

Enough to place the part where the song wants it, judged with the band playing. Start with less than sounds right solo, and compare with a reference in the same style.

Train it

Hear the room around the part.

Match the Space plays a part in a reference room. Rebuild it with a send fader and a decay pot: how much room, and how long it hangs on. Every setting plays at the same loudness.

Start Match the Space

Then: Front to Back, placing a part by distance · both part of Mix Chops Pro