The formula
The duration of a quarter note (1/4) in milliseconds is 60,000 ÷ BPM. All other values derive from this one:
- 1/2 = 1/4 × 2; a bar in 4/4 = 1/4 × 4
- 1/8 = 1/4 ÷ 2; 1/16 = 1/4 ÷ 4; 1/32 = 1/4 ÷ 8; 1/64 = 1/4 ÷ 16; 1/128 = 1/4 ÷ 32
- Dotted = value × 1.5 (dotted 1/8 = 1/4 × 0.75)
- Triplet = value × 2/3 (1/8 triplet = 1/4 ÷ 3)
In FL Studio, Fruity Delay 3 and Fruity Reeverb 2 (pre-delay) can be synced to tempo; when a plugin accepts only milliseconds, use the table.
Time table (ms)
| BPM | 1/4 | dotted 1/8 | 1/8 | 1/4 triplet | 1/16 | 1/64 | 1/128 | 1/2 | bar |
|---|---|---|---|---|---|---|---|---|---|
| 70 | 857 | 643 | 429 | 571 | 214 | 54 | 27 | 1714 | 3429 |
| 80 | 750 | 563 | 375 | 500 | 188 | 47 | 23 | 1500 | 3000 |
| 90 | 667 | 500 | 333 | 444 | 167 | 42 | 21 | 1333 | 2667 |
| 100 | 600 | 450 | 300 | 400 | 150 | 38 | 19 | 1200 | 2400 |
| 110 | 545 | 409 | 273 | 364 | 136 | 34 | 17 | 1091 | 2182 |
| 120 | 500 | 375 | 250 | 333 | 125 | 31 | 16 | 1000 | 2000 |
| 124 | 484 | 363 | 242 | 323 | 121 | 30 | 15 | 968 | 1935 |
| 128 | 469 | 352 | 234 | 312 | 117 | 29 | 15 | 938 | 1875 |
| 140 | 429 | 321 | 214 | 286 | 107 | 27 | 13 | 857 | 1714 |
| 150 | 400 | 300 | 200 | 267 | 100 | 25 | 12 | 800 | 1600 |
| 160 | 375 | 281 | 188 | 250 | 94 | 23 | 12 | 750 | 1500 |
| 174 | 345 | 259 | 172 | 230 | 86 | 22 | 11 | 690 | 1379 |
For trap and drill at 140–150 BPM with a half-time feel, delays of 1/4 and 1/8 work like the 1/8 and 1/16 of the half-time pulse.
Reverb pre-delay
Pre-delay is the time between the direct sound and the start of the tail. It serves to separate the source from its reverb: the vocal stays in front and the tail is heard behind.
- Musical values: 1/64 or 1/128 of a bar, that is 10–60 ms. At 120 BPM: 1/128 = 16 ms, 1/64 = 31 ms. At 90 BPM: 21 and 42 ms.
- Pop vocal: 20–40 ms (1/64 at 90–150 BPM).
- Vocal in a slow ballad: 40–80 ms (1/32 at 70–90 BPM: 107–94 ms is the limit beyond which the pre-delay is heard as an echo).
- Snare: 0–15 ms for a reverb attached to the hit; 20–30 ms for a snare that “blooms” after the attack.
- Background instruments and pads: 0–10 ms, you want them behind.
- Beyond 80–100 ms the pre-delay stops being perceived as separation and becomes a distinct echo.
Reverb length (decay)
A rule of thumb: have the tail end (down to −60 dB, or when it is no longer audible in the mix) within a musical value.
- Decay ≈ musical value − pre-delay. Example at 100 BPM, tail within 1/2 (1200 ms) with a pre-delay of 38 ms: decay ≈ 1160 ms.
- Snare: tail within 1/4 or 1/2 (the tail must close before the next hit).
- Pop vocal: tail within 1/2 or one bar in the choruses; shorter in the verses.
- Ballad: 1–2 bars.
- In a dense mix the ear hears only the first 20–30 dB of the tail: the “musical” decay can exceed the theoretical value.
Delay: typical choices
| Use | Time | Feedback | Notes |
|---|---|---|---|
| Slapback on rock/rockabilly vocal | 80–140 ms (not synced) | 0–10% | Mono, LP 3–5 kHz |
| Pop vocal delay | 1/4 or dotted 1/8 | 15–30% | HP 200–300 Hz, LP 4–6 kHz, sidechain from the vocal |
| Throw at the end of a phrase | 1/4 or 1/2 | 30–50% | Send automation |
| Ping-pong on synths and guitars | 1/8 or dotted 1/8 | 20–40% | Width without reverb |
| “Dub” delay | dotted 1/4, 1/2 | 50–80% | Filters and saturation in the loop |
| Artificial double (ADT) | 15–35 ms | 0% | With slight modulation |
Common mistakes
- Zero pre-delay on a vocal with a long reverb: the vocal recedes and loses intelligibility.
- Synced delay but with high feedback and no filters: the repeats accumulate mud and harshness.
- Reverbs longer than the time between two snare hits: the drums lose definition.
- Calculating times on the wrong BPM (project at 140 with a 70 feel): repeats that are out of the groove.
Starting settings
| Parameter | Value | Why |
|---|---|---|
| Formula | 60,000 ÷ BPM = 1/4 in ms | Basis of all times. |
| Vocal pre-delay | 1/64 of a bar (20–40 ms) | Separation between vocal and tail. |
| Maximum pre-delay | About 80–100 ms | Beyond that it becomes a distinct echo. |
| Snare decay | Tail within 1/4 or 1/2 | It closes before the next hit. |
| Pop vocal delay | 1/4 or dotted 1/8, feedback 15–30% | Depth in time. |
| Slapback | 80–140 ms, feedback 0–10% | Thickness without an obvious echo. |
Frequencies to watch
| Range | What to do |
|---|---|
| 150–300 Hz | HP on delay and reverb returns: the repeats do not add mud. |
| 2–6 kHz | Cut or ducking on the reverb return: the direct vocal stays more intelligible than the tail. |
| 4–6 kHz | LP on vocal delays: darker repeats that sit behind. |
Example chain
| Step | Tool | Settings | Why |
|---|---|---|---|
| Send | Return mixer track | Pre or post fader | Shared reverbs and delays. |
| Delay or reverb | Fruity Delay 3 / Fruity Reeverb 2 / Valhalla | 100% wet, times from the table | Space in time. |
| Return EQ | Fruity Parametric EQ 2 | HP 150–300 Hz, LP 5–10 kHz | Clean tail. |
| Ducking | Fruity Limiter with sidechain from the vocal | 2–4 dB | The tail opens up in the pauses. |
How to check the result
- High-bass and Low-mid bands of the mix: with the sends active, relative energy must not rise by more than 1 dB (filtered returns).
- In the Mid band (500 Hz–2 kHz) Side/Mid width increases with the reverb: values above −4 dB indicate a reverb that is too loud or too wide.
- Mix crest factor unchanged within 1 dB with and without effects: tails that are too long fill the pauses and reduce the crest factor.
- Listening in mono: ping-pong delays and reverbs must not vanish completely nor cover the vocal.