Tempo – the measure of time in music
Rhythm arranges the notes in time – but how fast this time itself passes is determined by tempo. It is the building block that gives a piece its basic feeling: the same written notes can sound as a calm lullaby or a breathless whirl, depending on how fast the pulse beats.
What tempo means
Tempo is the speed of the underlying pulse – that is, how fast the basic beats follow one another that you feel when clapping along. It can be given precisely in beats per minute (bpm): 60 bpm means one beat per second, 120 bpm twice as fast. This number determines how briskly the music moves, quite independent of which note values are being played just now.
It is important not to confuse tempo with note density: a slow piece can contain many fast notes and a fast piece long notes. Tempo concerns only the pulse in the background, not the amount of notes in the foreground.
The tempo markings
Traditionally tempi are given with Italian terms that mean not only the speed but often a character too. From slow to fast, for instance: Largo (broad, very slow), Adagio (calm, slow), Andante (walking, at a walking pace), Moderato (moderate), Allegro (fast, lively), Vivace (brisk) and Presto (very fast). These words are elastic and leave the performer room – "Andante" describes an attitude of calm walking rather than an exact value. It is precisely for this reason that a bpm number is often added in modern notation, to fix the tempo intended.
When time stretches
Music rarely stays strictly the same speed. The gradual growing faster is called accelerando, the gradual growing slower ritardando – both are strong means of expression: acceleration drives and intensifies, deceleration calms or announces a close. At the end of many pieces stands a ritardando that prepares the close, like a train rolling gently into the station. Finer still is rubato: a free, slight stretching and pressing of time in the service of expression, which gives the playing humanity and distinguishes it from rigid mechanics.
Tempo in numbers
For a long time there was no objective measure for tempo – the Italian terms were all composers had, and an "Allegro" could turn out noticeably different from player to player. That changed with the metronome, a device that makes an even, adjustable underlying beat audible, given in beats per minute. With it a tempo could for the first time be recorded and passed on unambiguously. To this day the metronome is the most important practice tool there is: it mercilessly reveals where you unconsciously grow faster or slower, and forces that evenness which is the basis of all secure playing. The tried-and-true way when learning a piece: practise a difficult passage at a tempo at which it succeeds without mistakes, and set the metronome higher only then, step by step. In this way tempo is not forced but grows out of security.
Tempo and character: the dances
The connection of tempo and character becomes especially vivid in the dances, from which a large part of music history has grown. A march lives off a firm, middling stride that invites walking together; a waltz swings in a flowing triple metre whose tempo is chosen just so that couples can turn; a minuet is measured and dignified, a gigue fast and springing. In all these cases the tempo is not arbitrary but belongs inseparably to the essence of the dance – to change it by a metronome number would destroy the character, just as a waltz played too slowly is no longer fit for dancing. Beyond the dances too this experience holds: every piece has a "right" tempo in which its motion seems natural – too fast it seems rushed, too slow sluggish. To find this right measure is one of the finest tasks of music-making.
Why tempo has such a strong effect
Tempo reaches directly into our bodily feeling, because we connect it with heartbeat, breath and movement. Slow tempi seem calm, sustained, often solemn or heavy; fast tempi seem excited, cheerful, urgent. That is why the choice of tempo alone can decide the character of a piece – and why it is so instructive, when practising, to play the same passage deliberately at different tempi and hear how its expression transforms. A tried-and-true practice principle here is: first slow and clean, then step by step faster – tempo is the reward for accuracy.
Remarkable too is how much the perceived tempo depends on the interplay with the other building blocks. Dense, small note values make a piece seem faster than its bpm number would suggest; long, calm notes seem slower. A driving rhythm, an urgent harmony or a crescendo can create the impression of acceleration without the pulse actually changing. Tempo is thus not only a measurable quantity but also a feeling that arises from the whole – the last of the seven building blocks, which at the same time sets all the others in motion.
Seven building blocks, one music
Rhythm, melody, harmony, dynamics, timbre, form and tempo – all music is built from these seven building blocks. Whoever knows them no longer merely hears that a piece has an effect, but understands why.