Delay Time Calculator

Tempo-synced delay converts a musical note value into a time interval. One quarter note lasts 60000 divided by the BPM in milliseconds, and every other subdivision is that figure scaled by a fixed multiplier: 4 for a whole note, 2 for a half, 0.5 for an eighth, 0.25 for a sixteenth. A dot adds half the note value, so dotted multipliers are 1.5 times the straight ones, while a triplet divides a value into three instead of two and multiplies by two-thirds. At 120 BPM this gives 500 ms for a quarter, 375 ms for a dotted eighth, and 166.67 ms for a triplet eighth. The same interval can be expressed in samples by multiplying milliseconds by the sample rate in kHz, 44.1 or 48, which is how sample-accurate plugins and some hardware express delay, or as a frequency in hertz by dividing 1000 by the delay in milliseconds. Perceptual thresholds decide what a given number actually sounds like. Below roughly 30 ms the ear fuses the delayed copy with the original rather than hearing a discrete echo, and the summation produces comb filtering with cancellation notches spaced across the spectrum, which is the mechanism behind flanging and chorus. Between about 1 and 35 ms the precedence effect places the apparent source at the earlier arrival, a fact exploited for stereo width. Slapback delay lives around 75 to 175 ms with little or no feedback, and reverb pre-delay is commonly set between 20 and 80 ms, often at a 1/64 or 1/32 note value, to keep the direct sound legible before the tail begins. The main caveats are that these figures assume a steady tempo, so material recorded to a human performance rather than a click will drift out of alignment, and that analog tape and bucket-brigade units cannot hold a calculated value precisely.

Delay began as a byproduct of tape machines. On a recorder with separate record and playback heads, the playback head reproduces what the record head laid down a fraction of a second earlier, and feeding that signal back produces repeats. Les Paul experimented with the effect in the late 1940s, and it entered popular music decisively at Sun Records in Memphis, where Sam Phillips used a second tape machine to put the short slapback echo on Elvis Presley 1954 sessions that became a defining rockabilly sound. Purpose-built units followed: Ray Butts built echo into his EchoSonic amplifier, Mike Battle and Don Dixon introduced the Echoplex in 1959 with a sliding head that let players vary delay time continuously, and Roland released the RE-201 Space Echo in 1974 with multiple playback heads for rhythmic patterns. On the theoretical side, Helmut Haas described the precedence effect in his 1949 dissertation, giving engineers a framework for what short delays do to perceived localisation. Exact millisecond values only became settable when delay went digital. Digital delay lines appeared in professional studios in the early 1970s from manufacturers including Lexicon and Eventide, replacing a sliding tape head with a numeric readout and making arithmetic like 60000 divided by BPM immediately useful. The MIDI specification of 1983 added a shared clock so that effects could follow a sequencer tempo automatically, and modern plugins simply read host tempo. The dotted eighth setting became the best known application of the calculation through The Edge of U2, whose cascading guitar parts on records of the early 1980s depend on repeats falling between the straight eighths, producing an interlocking pattern from a single played note.