Tempo
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When musicians communicate ‘beats per minute’ they aren’t expressing time per se but rather what is called ‘tempo’. The Italian word ‘tempo’ literally translates to ‘time’ and it is used to describe the ‘speed’ of a passage, melody, or song. It is mostly a way to indicate the ‘stable speed’ however there are also specific terms to indicate an acceleration or deceleration of tempo/speed. ‘Beats per minute’ literally describes how many beats (ticks, taps, claps etc) occur within a minute. For example, 70bpm means that if you start a stop watch and start counting the number of clicks or taps you hear over 60 seconds, the result would be 70 taps per minute. This is the same unit of measurement used when a doctor measures a heart beat or pulse. A person who has a heart rate of 70bpm or a pulse of 70bpm has 70 pulses or beats per 1 minute. If a pulse were to either decrease or increase drastically, a doctor could tell that something out of the ordinary might be occurring in a patient. I like the analogy of ‘beat’ to ‘pulse’ because a beat gives the impression that it can occur only once. A beat can be a hit, while a pulse gives the impression that it is a repeating event which is much closer to what is occurring in music. Still, the correct term for measuring tempo is ‘beats’ per minute.
In music, the tempo of a song reflects the composer’s or conductor’s intended pulse of a song and therefore the expected pulse or speed they expect the performing musicians to play at for everyone to play in sync with one another.
*Interesting note about composers and why they exist:
Have you ever wondered why some guy waving his hands and arms (the composer) is needed when music is being performed by orchestras? Is the conductor just some crazy person who is attempting to dance to the music? Why does he sometimes seem upset and why does he dance with only his arms and not his hips or legs? Does he even play an instrument or is he someone’s crazy uncle who just tags along with the rest of the band?
Well, the conductor’s role is actually very important to the orchestra as he/she is the time keeper for the whole orchestra. Since orchestras can be very large and can contain any number of musicians spread apart or at least seated away from one another in a large theater, the musician sitting at the far right will not hear the music being performed by the musician at the far left, just as the musicians in the middle might have trouble hearing musicians from either side. The reason is that sound does not travel very fast therefore there would be a delay in sound before a musician in the middle hears a musician on the far left or right of them (and vice versa) which would mean that musicians would constantly play out of time. Similar to thunder and lightning, you always see lightning before you hear thunder. The two have actually occurred at the same moment however since light travels much faster than sound, you will experience the lightning before you will hear the thunder. Since this is the case, musicians will rely on what they see, the composer, rather than what they hear for them to play on time. Since everyone, regardless of where they are sitting, focuses on the composer’s movements (assuming they can see the composer), they now have a reference, a tempo, to follow and will all be synchronized to one another. A musician will never be so far away that they will experience a delay in what they see since light is that much faster than sound. In addition, the composer can provide other visual cues, either through emotions or perhaps with the use of the other arm, that might otherwise be too complicated to provide musicians through a different means.
The tempo is therefore the speed or pulse of a piece of music. As previously mentioned, the speed can fluctuate, since increasing or decreasing speed can help convey a sense of calm or urgency, however the tempo is usually stable for at least a couple of measures or bars before it changes (if it changes at all) since tempo is specifically there to help keeps musicians synchronized. An unstable tempo is counter-intuitive and even if it were to increase in speed, there would still be a controlled stability which would allow musicians to move at the same pace as one another.
