One note name, three times
“Eighth note delay” is not a setting. It is three settings, and which one is meant is usually left to the reader.
The same note values at 120 BPM, in milliseconds| Note | Straight | Dotted | Triplet |
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| Half | 1000 | 1500 | 666.7 |
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| Quarter | 500 | 750 | 333.3 |
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| Eighth | 250 | 375 | 166.7 |
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| Sixteenth | 125 | 187.5 | 83.3 |
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The two modifiers are simple and exact. A dot adds half the note’s own value again, so a dotted note is 1.5 times the straight one — a dotted quarter is a quarter plus an eighth. A triplet fits three notes into the space two would occupy, so each is two thirds as long, and three of them add up to exactly the undivided value.
Those relationships hold at every tempo and every note value, which is why this page prints all three columns rather than putting the modifier behind a menu. The difficulty is not the arithmetic; it is that the three answers share a name.
The hertz column matters for anything that modulates rather than repeats. A tremolo, an auto-panner or an LFO is set in cycles per second, and a quarter note at 120 BPM is exactly 2 Hz. Milliseconds and hertz are reciprocals of one another, so the same table serves both.
The dotted eighth and the triplet quarter
Of all the pairs on that grid, two get confused constantly, and it is worth seeing exactly how close they are.
At 120 BPM a dotted eighth is 375 ms and a triplet quarter is 333.3 ms. Forty-two milliseconds apart — close enough to sound similar on their own, and completely different against a track, because one locks to the grid and the other pulls against it.
The proportional gap is 12.5%, and it is 12.5% at every tempo. That is not a coincidence of 120 BPM: it is the ratio of the two modifiers, 1.5 against 2/3 applied to different base values, so it is fixed. What does change with tempo is the gap in milliseconds — 83 ms at 60 BPM, 25 ms at 200 — so the faster the track, the harder the mistake is to hear and the more it still matters.
The dotted eighth is the one behind most of the delay sounds people are trying to reproduce. It creates a repeat that lands between the beats in a way that feels propulsive rather than doubling, which is exactly why it became a cliché. A triplet quarter in its place produces something rhythmically quite different and generally less useful against a straight track.
Two habits avoid the whole problem. Write down which modifier you meant, since “dotted 1/8” is unambiguous and “1/8 delay” is not. And when a device offers note values directly, check whether its dotted and triplet options are labelled or only symbolised — a dot and a small 3 are easy to miss on a small screen.
Tempo and time are reciprocals
Beats per minute and milliseconds per beat are inverses, which means equal steps in one are unequal steps in the other. It catches people out because tempo feels linear.
What the same ten beats per minute is worth| Change | Beat goes from | Shortens by |
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| 60 → 70 | 1000 → 857 ms | 143 ms |
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| 100 → 110 | 600 → 545 ms | 55 ms |
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| 140 → 150 | 429 → 400 ms | 29 ms |
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| 170 → 180 | 353 → 333 ms | 20 ms |
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The same ten BPM is worth seven times more at the slow end than the fast end. So nudging a ballad from 60 to 70 is a large change to how much room there is between hits; nudging a fast track from 170 to 180 is a comparatively small one, even though the number moved by the same amount.
This is the same shape as the fuel-economy illusion, where going from 10 to 20 miles per gallon saves far more fuel than going from 30 to 50. Any time a quantity is per something, equal steps in the rate are curved steps in the thing itself.
The practical version: if you are matching two tracks and one is at 90 while the other is at 96, that six BPM is worth 44 ms per beat — audible and awkward. The same six BPM between 170 and 176 is 12 ms, which is close to nothing. Judge tempo differences by their time value, not their number.
What feedback actually controls
A delay’s feedback control sets how much of each repeat is fed back in. The knob is linear; what you hear is not.
Each repeat multiplies the level by the feedback fraction, so the number of audible repeats grows logarithmically. Taking “audible” as 60 dB below the first repeat, which is the usual convention:
Repeats to −60 dB, and the tail at a 375 ms delay| Feedback | Repeats | Tail |
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| 30% | 5.7 | 2.1 s |
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| 50% | 10.0 | 3.7 s |
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| 70% | 19.4 | 7.3 s |
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| 85% | 42.5 | 15.9 s |
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Going from 30% to 50% roughly doubles the tail. Going from 70% to 85% roughly doubles it again, on a much larger number — so almost all the useful range sits in the last quarter of the control, and small movements up there change the sound far more than small movements lower down.
At 100% the repeats never decay at all. That is not a very long delay; it is a runaway, and it is why this calculator refuses the value rather than returning a large number. Analogue units that self-oscillate at high settings are doing exactly this on purpose, and it is a sound rather than a setting.
Worth remembering that the tail is also linear in the delay time. Doubling the delay at the same feedback doubles how long it rings, so a slow dotted-quarter delay at a modest feedback can ring for longer than a fast sixteenth at a high one.
Using these numbers in practice
The arithmetic is exact and music is not, so a few notes on where the two part company.
- Reverb pre-delay uses the same table. Setting pre-delay to a sixteenth or a thirty-second at the track tempo keeps the reverb’s onset out of the way of the transient. At 120 BPM those are 125 and 62.5 ms.
- Below about 30 ms a repeat stops being an echo. It fuses with the original and is heard as tone colour or as width instead. That is the territory of doubling and comb filtering rather than delay, and note values that short are usually being used for their timbre.
- Swing is the deliberate refusal of this grid. Swung eighths are unequal by design, sitting somewhere between straight and full triplet feel, so a delay locked to the straight value will fight a swung part. The triplet column is the closest fixed approximation.
- Set the number, then move it. Players sit ahead of or behind the grid on purpose, and a delay that is mathematically correct can still sit awkwardly. The calculated value is where to start, not where to stop.
One last practical point about tempo markings. The Italian terms overlap deliberately — 120 BPM is both Moderato and Allegro depending on the edition, and Vivace and Presto share most of their range. They were descriptions of character before the metronome existed, and treating them as tempo ranges is a modern retrofit. That is why the calculator shows every marking a tempo falls under rather than picking one.
Sources and methodology
Almost everything on this page is arithmetic rather than convention — a quarter note at a given tempo has one length and no standards body is needed to say so. The sources cover the two parts that are not: the perceptual thresholds behind when a repeat is heard as an echo, and the −60 dB convention used to describe how long a decaying tail lasts.