BPM (Beats per minute) is a measure of the tempo of the song. In music written with a traditional score a particular note value (for example, a quarter note, or crotchet) is specified as the beat, and that the amount of time between successive beats is a specified fraction of a minute. The greater the number of beats per minute, the smaller the amount of time between successive beats, and thus faster a piece must be played.
BPM is particularly import in dance music because of its usefulness to DJs. In this context the beats measured are either quarter notes in the time signature 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, trance music ranges from 125 to 150 BPM, and drum and bass generally ranges between 150–180 BPM.