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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.

The BPM tempo of a piece of music is conventionally shown in its score as a metronome mark, as illustrated to the right. This indicates that there should be 120 crotchet beats (quarter notes) per minute. In simple time signatures it is conventional to show the tempo in terms of the note duration on the bottom. So a 4/4 would show a crotchet (or quarter note), as above, while a 2/2 would show a minim (or half note).

In compound time signatures the beat consists of three note durations (so there are 3 quavers (eighth notes) per beat in a 6/8 time signature), so a dotted form of the next note duration up is used. The most common compound signatures: 6/8, 9/8, and 12/8, therefore use a dotted crotchet (dotted quarter note) to indicate their BPM.

Exotic time and particularly slow time signatures may indicate their BPM tempo using other note durations.

Dance music

Template:Sound sample box align right

Template:Sample box end Beats per minute became common terminology in disco because of its usefulness to DJs, and remain important in the same genre and other dance music.

In this context the beats measured are either crotchets (quarter notes) in the time signature (sometimes called down-beats, although the term is ambiguous), or drum beats (typically bass-drum or another functionally similar synthesized sound), whichever is more frequent. Higher BPM values are therefore achievable by increasing the number of drum beats, without increasing the tempo of the music. House music is faster around 120-128 bpm (from regular house music to UK Garage), and Jungle music generally ranges between 140-150 bpm (with some differences in older compositions). Psytrance is almost exclusively produced at 145 BPM, whereas Speedcore and Gabber music both frequently exceed 160 BPM, with an underlying crotchet tempo of around 150-220 BPM .

Extreme BPM

More extreme BPMs are achievable at the same underlying tempo with very fast drum patterns, often expressed as drum rolls. Such compositions often exhibit a much slower underlying tempo, but may increase the BPM by adding additional percussive beats. Extreme music subgenres such as speedcore and cybergrind often strive to reach excessively high BPM rates.

Beatmatching

Beatmatching, 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 seamlessly mixed.

DJs often beatmatch the underlying tempos of recordings, rather than their strict BPM, particularly when dealing with high BPM tracks. A 240 BPM track, for example, will normally match the beat of a 120 BPM track without slowing down or speeding up, because both are likely to have an underlying tempo of 120 crotchets (quarter notes) per minute. Thus, some soul music (around 75-90 beats per minute) can be mixed well with a drum and bass beat (from 150-185 beats per minute).

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 processing to change the pitch without changing the tempo, or vice-versa, is called time-stretching or pitch-shifting. While it works fairly well for small adjustments (± 20%), the result can be noisy and unmusical for larger changes.

BPM can be calculated manually by counting the number of bass drums per 60 seconds, or per 15 seconds and multiply by 4 (method cannot function with breakbeat-style genres such as drum n bass, dubstep, or hip hop, and can only work with electronic styles with four-to-the-floor beats such as House, UK Garage, and Trance), but some software programs can do it automatically by listening for regular volume peaks at low frequencies. CD turntables such as the Pioneer CDJ-1000MK3 also have an automatic BPM counter, as do some DJ mixers. Some software is able to use complex algorithms based on granular synthesis to achieve more complicated beat matching with tonal and multitimbral waveforms.

References

External link

• All8.com's - Beats Per Minute counter Tap computer key to the beat

• Musical terminology
• Units of frequency