Beats per minute (bpm) is a unit typically used as either a measure of tempo in music, or a measure of one's heart rate. A rate of 60 bpm means that one beat will occur every second. One bpm is equal to 1/60 Hz.
Beats per minute became common terminology in popular music during the disco era because of its usefulness to DJs, and remain important in dance music.
Hip-hop uses a BPM tempo of 90-120, while house music is faster: 110 -140BPM. Jungle music goes even faster: 140-190, while Gabba tops it with above-200 BPM and Speedcore with 200-700 BPM.
Beatmixing, an art amongst DJs, concerns the speeding up or down of a record in order to match the BPM of a previous track so both can be flawlessly mixed.
Normally, the pitch and BPM of a track are linked: spin a disc 10% faster and both pitch and tempo will be 10% higher. Software to change the pitch without changing the tempo, or vice-versa, is called time-stretching or pitch-shifting software. It works OK for small adjustments (+- 20%), but the result can be noisy and unmusical for larger changes.
BPM can be calculated by hand (count the number of downbeats/bass drums per 60 seconds, or - to be fast - per 15 seconds and multiply by 4), but some softwares like MixMeister, Traktor-DJ and PC-DJ can do it automatically.
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