In measuring the speed of a car, we can look at the number of miles it can travel in an hour (mph). If we were measuring the speed of a boat, it would be measured in knots per hour (kph). In measuring the internal workings of the engine, we can measure the number of revolutions per minute (rpm). When it comes to examining the speed of music, the unit of measurement is the single beat, and the length of time is a minute; therefore, musical speed is measured in beats per minute (bpm).
In order to measure bpm, a person can count the number of beats or strong, consistent pulses in one minute. However, a much simpler method would be to count the number of pulses or beats that are in ten seconds and then multiply by six to find the number in 60 seconds or one minute.
In example A, the number of beats or pulses in ten seconds are 10, so the bpm would be (10 x 6=) 60 bpm. Example B is much faster, registering 15 beats in the same 10 seconds, or 90 (15 x 6) bpm. Example C is faster yet, with 20 beats in 10 seconds for a speed of 120 bpm.
Example A (60 bpm):
Example B (90 bpm):
Example C (120 bpm):
The word used for speed in music is tempo, which is an Italian word rooted in the Latin word “tempus” or time. So, when we talk about the speed of music, we speak of the tempo at which it is being played. Example A had a tempo of 60 bpm; Example B was being played at 90 bpm; and Example C had a tempo of 120 bpm.
It is important to note that songs rarely stay at one steady tempo throughout the entire music. Often a song may change speeds or tempi (plural of tempo) suddenly, perhaps with a change from verse to chorus, or with the introduction of a new emotional lyric. More frequently, music changes tempo gradually, either speeding up, which may signify an increase in excitement or energy; or slowing down, creating a feeling of contemplation or possibly sadness.
Tempos and tempo changes are important in creating the proper “feel” of the music; therefore, performers have a responsibility to choose the most appropriate tempos and tempo changes to communicate to the listener. A tempo taken too fast can be absurd and silly, while a tempo too slow may be bogging and funereal.