BPM to reverb pre-delay: give the dry sound room

At 120 BPM, a sixty-fourth note is 31.25 ms, a thirty-second is 62.5 ms, and a sixteenth is 125 ms. These are useful timing references for reverb pre-delay, but they describe a musical interval, not a requirement for a good mix.

Pre-delay is the gap between the dry sound and the beginning of the reverberant response. A short gap can separate a vocal’s consonant or a drum’s attack from the reverb around it. A longer gap can become an audible echo, particularly on a sharp transient.

Find a small musical subdivision

First calculate a quarter-note beat: 60,000 / BPM. Divide that duration by 8 for a thirty-second note, by 16 for a sixty-fourth, or by 32 for a one-hundred-twenty-eighth note.

BPM	1/128 note	1/64 note	1/32 note
90	20.833 ms	41.667 ms	83.333 ms
120	15.625 ms	31.250 ms	62.500 ms
150	12.500 ms	25.000 ms	50.000 ms

Open the BPM calculator, enter the session tempo, and read those rows in the Straight column. Use three-decimal precision if your plugin supports it. Dotted and triplet values are also available when you want to try an interval between the straight subdivisions.

Set pre-delay while listening to the source

1. Choose the reverb character and a moderate decay first, so you can hear what the gap changes.
2. Start with a shorter calculated value, such as 15.625 or 31.25 ms at 120 BPM.
3. Compare the dry attack with the onset of the reverb. Increase the gap if the attack is being blurred, or reduce it if a separate echo becomes distracting.
4. Check the part in the mix, including pauses and phrase endings. A setting that sounds dramatic in solo may crowd the next phrase.

Listen at a useful working level and adjust the reverb send as well. Pre-delay cannot compensate for excessive wet level, an overly long tail, or a frequency buildup in the reverb return.

Decay is a separate parameter

Decay describes how the reverberant energy fades. Some processors label it as RT60 or T60: an approximate time for the level to fall by 60 dB. Others use a different definition or a relative control. Check the plugin’s documentation before treating its value as an exact endpoint.

At 120 BPM, a half note is 1,000 ms and a whole note is 2,000 ms. In a 4/4 passage, the whole note also spans one bar. Those durations can help you compare shorter and longer tails in context, but a reverb does not suddenly stop at its displayed decay time. Its envelope, damping, diffusion, and the input material all affect what you hear.

If the decay field uses seconds, divide the calculator result by 1,000. For example, 1,500 ms is 1.5 seconds. Do not paste 1,500 into a field expecting seconds.

Should pre-delay and decay add up to a bar?

They can be used that way as an experiment, but it is not a general mixing rule. A mathematically aligned total does not guarantee that the tail clears the next hit or lyric. A dense phrase may need a much shorter tail; an ambient transition may benefit from one that extends across several bars.

Use the calculated timings to choose reproducible starting points, then let the source and arrangement decide. For distinct rhythmic echoes, use the delay-time workflow. For how dotted and triplet choices relate to a straight note, see note timing explained.