Tempo Markings and Tempo Change

Tempo is the speed of the beat, and composers mark it two ways. Italian words like largo, andante, allegro, and presto describe a general feel, built from centuries of shared usage, so largo feels slow because musicians have always treated it as a broad, spacious pace, not because a number demands it. Metronome markings give an exact number: quarter note equals 90 means 90 quarter notes happen every minute, so each quarter note lasts 60/90 seconds. The two systems describe the same reality at different levels of precision, one a tradition, the other a measurement.

Once you know the beat duration, you can find how long any measure lasts, because a time signature tells you how many beats fill the measure. In 3/4 time, each measure holds three quarter-note beats, so the measure's length is just three times the length of one beat. This is where tempo stops being a feeling and becomes arithmetic: seconds per beat times beats per measure gives seconds per measure.

Tempo markings also change mid-piece, through sudden shifts like piu mosso or gradual ones like accelerando and ritardando, and comparing two metronome numbers lets you calculate exactly how much faster or slower the new tempo is. This sets up the next layer of expression: dynamics and articulation, which shape loudness and attack the way tempo shapes speed, together giving a performer the full picture of how a piece should move and breathe.