A quarter-note delay lasts 60,000 divided by the BPM, in milliseconds; other note values are multiples and fractions of that. Reverb has two timings: the pre-delay, a short gap before the reverb starts, and the decay, the time the tail takes to fade. Setting them in relation to the tempo keeps echoes on the beat and stops the reverb from blurring the next phrase.
In Short
The short version:
- Quarter note in ms = 60,000 ÷ BPM.
- Dotted = × 1.5; triplet = × 2/3.
- A pre-delay of 20 to 40 ms keeps vocals clear.
- Let the reverb fade before the next phrase.
- The numbers are starting points; the final judge is the ear.
The Delay Time Formula
A delay repeats the sound after a set time. When that time matches a note value of the song, the repeats fall on the beat and become part of the rhythm; when it does not, they land between the beats and clutter it. The calculation starts from one beat: there are 60,000 milliseconds in a minute, so a quarter note lasts 60,000 divided by the tempo in BPM.
At 120 BPM that is 500 ms. An eighth note is half of it, 250 ms, and a sixteenth 125 ms. A dotted note is one and a half times its plain value, so a dotted eighth is 375 ms; a triplet eighth is a third of the quarter note, 166.7 ms.
| Note value | Formula | At 100 BPM | At 120 BPM | At 140 BPM |
|---|---|---|---|---|
| Quarter | 60,000 ÷ BPM | 600 ms | 500 ms | 428.6 ms |
| Eighth | Quarter ÷ 2 | 300 ms | 250 ms | 214.3 ms |
| Dotted eighth | Eighth × 1.5 | 450 ms | 375 ms | 321.4 ms |
| Eighth triplet | Quarter ÷ 3 | 200 ms | 166.7 ms | 142.9 ms |
| Sixteenth | Quarter ÷ 4 | 150 ms | 125 ms | 107.1 ms |
Which Delay Time to Choose
- Quarter and eighth notes give plain echoes that sit on the beat. They suit vocals and lead lines with room around them.
- Dotted eighths fall between the beats and create a rolling pattern; with one or two repeats they thicken guitar and synth parts.
- Triplets pull against a straight rhythm and add a shuffle.
- Very short delays, around 80 to 120 ms with a single repeat, are heard as a slap-back echo and not as rhythm, so they need not follow the tempo.
Reverb: Decay Time and Pre-Delay
Reverb is the sum of a great many reflections, too dense to be heard separately. Acoustics measures it as reverberation time, or RT60: the time the sound in a room takes to fall by 60 decibels after the source stops, as McGill University’s course notes on room acoustics define it. The decay control of a reverb plugin sets the same thing for an imaginary room.
The second control that matters is the pre-delay, the pause between the dry sound and the first reflections. In a real hall it corresponds to the time sound needs to reach the nearest wall and come back. In a mix it has a practical use: with 20 to 40 ms of pre-delay, the start of each word or note is heard dry before the reverb arrives, and the vocal stays in front.
To relate both to the tempo, many engineers set them so that pre-delay plus decay equals a note length, for example one beat in a busy, fast song or one bar in a ballad. The reverb then fades just as the next beat or bar begins. It is a convention, not a law of acoustics, but it is a reliable place to start.
| Delay | Reverb | |
|---|---|---|
| What you hear | Separate repeats | A continuous tail |
| Main settings | Time, feedback | Pre-delay, decay |
| Effect in a mix | Rhythm and width | Depth and space |
| Risk | Clutter, if the time fights the tempo | Mud, if the decay is too long |
How to Set Delay and Reverb in 4 Steps
The whole procedure takes a minute once you know the tempo.
Step 1: Find the Tempo
Read it from your project, measure it with the BPM & Key Analyzer or tap it with the BPM Tapper.
Step 2: Calculate the Times
Enter the BPM in the Delay/Reverb Calculator. It lists every note value in milliseconds, with dotted and triplet versions, and suggests pre-delay and decay values for the reverb.
Step 3: Enter Them in Your Effects
Switch the delay from sync to time mode if you want a value the sync menu does not offer, and type in the milliseconds. Then set the pre-delay and the decay of the reverb.
Step 4: Listen in the Mix
Judge the effects with the whole track playing, not in solo. Shorten the decay or lower the effect level until the words are clear and the tail is gone before the next phrase.
Three Habits That Keep a Mix Clear
- Filter the effects: cut the low end of delay and reverb returns, and often some of the top as well. Bass in a reverb is the quickest way to a cloudy mix.
- Use sends: put delay and reverb on their own channels and send several tracks to them. The instruments then share one space, and the effect level is easy to control.
- Less than you think: set the effect where you just notice it, then turn it down a little. It should be missed when it is muted, not noticed when it is on.
Calculate Your Delay and Reverb Times
Enter a tempo and get every note value in milliseconds or hertz.
Open the Delay/Reverb CalculatorFree, no sign-up, and your files never leave your device.