Music also organizes these according to a framework called meter, by partitioning time into patterns of "strong" and "weak" beats.
If a file plays at a fixed tempo, its map is a horizontal line (e.g., measures 38 and 39 in this part of a MIDI sequencer’s display of the end of J.S.
But, if the tempo fluctuates as a function of time, such as in accelerando, allargando, or rubato, the line is respectively an upward- or downward-climbing one, or in the latter case, a complex curve, as seen here in measures 35 and 36 at left, or the ending in measures 40 and 41.
Hence, a very emotional piece such as the preceding is excerpted from, although playing at a base tempo of MM=50 — which means 50 quarter notes per minute, holding back or lunging forward according to expressive impulse can result in a tempo map similar to that seen above: It flexes tempo down for the intermediate cadence at left, and again for the final allargando at the right.
After recording a sequence in real time at a fixed tempo, or composing it using step-record mode, MIDI sequencer software may have functionality to edit the MIDI tempo map, so as to result in a natural, expressive result, not a machine-like one, when playing the file.