Tempo, time signatures and note timing

Tempo is the speed of the beat, measured in beats per minute (BPM). Time signatures and note values describe how those beats are grouped and divided.

Time signatures

A time signature has two numbers. The top number tells you how many beats are in a bar. The bottom number tells you which note value counts as one beat.

• 4/4: four quarter-note beats per bar. The default in most pop, rock and dance music.
• 3/4: three quarter-note beats per bar. The waltz feel: strong, light, light.
• 6/8: six eighth-note beats per bar, usually felt as two groups of three. This is a compound feel: each main beat divides into three rather than two, giving a rolling, swaying pulse.

Note values

Each note value is half the length of the one before it:

A dotted note is lengthened by half of its own value, so a dotted eighth equals 0.75 beats. A triplet fits three notes in the time of two, so an eighth-note triplet lasts one third of a beat.

Milliseconds per beat

The duration of one quarter-note beat is:

ms per beat = 60000 divided by BPM

At 120 BPM that is 500 ms. Other note lengths follow by multiplying.

At 90 BPM a quarter note is about 667 ms; at 140 BPM it is about 429 ms.

Using tempo for delay and reverb

Delay repeats that land on note divisions of the tempo blend into the groove instead of cluttering it. Many delay plugins have a sync option, but you can also type the millisecond value in. A dotted-eighth delay at 120 BPM is 375 ms, a common choice because the repeats fall between the beats.

For reverb pre-delay (the gap before the reverb starts), a sixteenth or thirty-second note at the song tempo is a common starting point. A short pre-delay keeps the dry sound clear while the tail follows in time. Treat these as starting values and adjust by ear.

Reverb and release times can be tuned the same way: a tail that decays by the next beat leaves space for the following note.

Typical tempo ranges

These ranges are typical, not absolute, and plenty of music falls outside them.

Half-time and double-time feels can make a track seem slower or faster than its BPM suggests.

Hear it yourself

Use the Idea Generator to produce a sketch, then change the tempo and notice how the same notes change character.

Open the Idea Generator