Tempo-Syncing Vocal Effects: Delay and Reverb Math
Vocal mixing · 4 min read
A quarter note in milliseconds is 60000 divided by the BPM. Divide by 2 for an eighth, by 4 for a sixteenth, by 8 for a thirty-second. Multiply any of those by 1.5 for dotted, or by 0.667 for a triplet. That single formula sets every delay, every predelay and every reverb decay in the session.
The formula
60000 / BPM
= one quarter note in milliseconds
The 60-second answer
Quarter = 60000 / BPM. Eighth = / 2. Sixteenth = / 4. Thirty-second = / 8. Dotted = x 1.5. Triplet = x 0.667. At 120 BPM: 500, 250, 125, 63 ms, dotted eighth 375, triplet eighth 167. At 140 BPM: 429, 214, 107, 54, dotted 321, triplet 143. One bar of 4/4 is 240000 / BPM.
Why sync buttons are not enough
Most plugins have a sync button, so why do the math? Three reasons. Analog-modelled delays often have a time knob in milliseconds and no host sync. Reverb predelay is almost never syncable but benefits from being on the grid. And decay is always in seconds, so the only way to relate it to the song is to know how long a bar is. Produce the number in five seconds and you stop guessing.
Why dotted and triplet values sound different
A straight eighth lands on the subdivision the hi-hat is already playing, so the repeat reinforces the groove and can disappear into it. A dotted eighth is one and a half eighths long, so it lands between the hits and resolves to the downbeat every three beats — the drifting delay sound on most modern records. A triplet eighth is two thirds of a straight eighth and pushes against the beat. Same delay, three different feels.
Using the math, step by step
| # | Do this |
|---|---|
| 01 |
Write the quarter note down once Open the calculator, do 60000 / BPM, and keep the number in the session notes. Everything else comes from it. 120 BPM → 500 ms |
| 02 |
Halve your way to the value you need Eighth is half the quarter, sixteenth is half again, thirty-second is half again. At 90 BPM: 667, 333, 167, 83 ms. /2, /4, /8 |
| 03 |
Multiply for dotted and triplet Dotted is x 1.5, triplet is x 0.667 (two thirds). At 150 BPM the eighth is 200 ms, dotted 300 ms, triplet 133 ms. x1.5 dotted · x0.667 triplet |
| 04 |
Use a thirty-second for reverb predelay At 120 BPM that is 63 ms; a sixty-fourth (/16) is 31 ms. The shorter value keeps the vocal tight, the longer one makes the tail a rhythmic event. Predelay: /8 or /16 |
| 05 |
Set slap delay from a thirty-second 60000 / BPM / 8 lands in the 60–120 ms slap window between roughly 63 and 125 BPM. Faster than that, use a 1/16 note. Slap: 1/32 note |
| 06 |
Convert reverb decay to bars One bar is 240000 / BPM. Divide your decay in ms by that to see what fraction of a bar the tail occupies. Bar = 240000 / BPM |
The trick: sync the reverb decay to a bar so the tail dies on the downbeat
Delay times get synced by everyone and reverb decay almost never does, which is strange, because the tail is the longest effect in the mix and the one most likely to run into the next section. Work out the bar length first: 240000 / BPM, so 2000 ms at 120 BPM, 1714 ms at 140 BPM, 2667 ms at 90 BPM. Set the reverb decay to exactly one bar, or half a bar for busy sections. Since decay is specified as the time for the tail to fall 60 dB, a one-bar setting means the reverb is effectively silent when the next downbeat arrives, so the tail resolves with the music instead of being cut off by it. This matters most on the last word of a section, where the tail runs out exactly as the new part begins. Use two bars for ambient sections and half a bar above 140 BPM.
Stop guessing the chain.
The Vocal Chain Bible is 88 real vocal chains from Grammy-winning engineers — every plugin, every setting, in order, with free alternatives for each one. 5+ years, 100+ interviews, one PDF.
Get the Vocal Chain Bible — $48 →Mistakes that kill it
- Using 60000 / BPM for an eighth note. That formula gives a quarter note. Halving twice for a sixteenth is where most arithmetic errors happen.
- Treating dotted as x 2. Dotted means one and a half times the value, so x 1.5. Triplet is two thirds, or x 0.667.
- Syncing to the wrong tempo. With a tempo map or a different click, host sync locks to the wrong grid. Check the number in ms.
- Syncing everything. A perfectly gridded delay on a free-time ballad intro sounds mechanical. The math is a starting point, not a rule.
Keep going
FAQ
What is the formula for delay time in ms?
60000 / BPM gives a quarter note. Divide by 2, 4 or 8 for eighth, sixteenth and thirty-second notes. Multiply by 1.5 for dotted, 0.667 for triplet.
What is a 1/8 dotted delay at 120 BPM?
375 ms. The eighth note is 60000 / 120 / 2 = 250 ms, and dotted is 250 x 1.5.
Should reverb be tempo synced too?
The decay should. Set it to one bar (240000 / BPM ms) or half a bar for busy sections so the tail resolves with the music instead of over it.
Who's behind this
Ivan Meshcheriakov · IvanFromRnD
5+ years ago I moved to LA with zero connections and started building from nothing — 14-hour days, meeting people and interning at studios. It took me 5+ years to meet and interview 100+ Grammy-winning engineers — then I turned it all into the Vocal Chain Bible.
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