Tempo Changes in Music: Accelerando, Ritardando, Rubato and Sudden Shifts

A plain-language guide to how and why the speed of music bends, stretches and jumps, and how a deliberate tempo change differs from simply rushing or dragging.

Short answer: a tempo change is any intended move from one speed to another. It can be gradual (accelerando to speed up, ritardando or rallentando to slow down), flexible and expressive (rubato, where a player borrows and repays small amounts of time within a phrase), or sudden (a tempo to snap back to the previous speed, meno mosso for "less motion," più mosso for "more motion"). A rarer, precise kind is metric modulation, where a note value from the old tempo becomes the pulse of the new one. What unites all of them is intention, which is exactly what separates a musical tempo change from unwanted rushing or dragging.

What counts as a tempo change

Tempo is how fast the underlying pulse moves, usually measured in beats per minute. If you are unsure how the felt speed relates to the notes on the page, our note on rhythm versus tempo untangles the two, and what BPM means covers the measurement itself. A tempo change, then, is any shift in that pulse rate that the music asks for on purpose. Grove Music Online notes that tempo indications historically carried both a speed and a mood, so a written change often signals a change of character as much as a change of clock rate. The important word is on purpose. A composer writes the change into the score, or a performer chooses it, and the whole ensemble moves together. That shared intent is the thread running through everything below.

Gradual change: accelerando and ritardando

The two workhorses are accelerando (getting faster) and ritardando or the near-synonym rallentando (getting slower). Both are smooth, continuous slides rather than steps, drawn in a score with the word plus a dotted line showing how far the change extends. We are surprisingly good at hearing these curves. A gentle accelerando raises tension and drive, while a ritardando releases it, which is why so many pieces slow down as they approach a cadence or a final chord.

The closing slowdown has attracted real study. Analyses of expressive performance suggest that a well-judged final ritardando often resembles a physical body coming smoothly to rest, with the tempo curve flattening as it approaches the end rather than braking abruptly. Related work on phrase timing shows that skilled players lengthen notes at the ends of phrases in consistent, repeatable ways, so the slowing is structured, not random. That structure is the tell. A musical ritardando has shape and returns the same way on a second performance; accidental dragging does not.

Rubato: flexible, expressive time

The most subtle tempo change is tempo rubato, Italian for "stolen time." Grove Music Online and Richard Hudson's history of the practice describe two overlapping senses. In the older, so-called earlier rubato, the melody pushes and pulls freely while the accompaniment holds a steady beat, so time is stolen from one voice and given back within the same bar. In the later, more familiar sense, the whole texture flexes together: the player lingers on an expressive note, then hurries slightly to make up the difference, so the phrase as a whole stays close to its underlying tempo.

Perception research helps explain why rubato sounds expressive rather than sloppy. Detailed measurements of pianists playing Romantic repertoire, including Bruno Repp's quantitative studies of timing, show that expert rubato is highly systematic. The lengthenings and shortenings cluster at phrase boundaries and structural high points, and different world-class players produce strikingly similar timing profiles. In other words, good rubato is not "playing without a pulse." It is a stable, learned pattern of departure from the pulse, which the listener reads as feeling. This is also why rubato is hard to fake: an unschooled wobble in tempo lacks that consistent, phrase-linked shape.

Sudden shifts: a tempo, meno mosso, più mosso

Not every tempo change is a gradual slide. Some are steps that happen from one beat to the next. After an accelerando or ritardando, the marking a tempo tells players to return to the previous speed at once. Meno mosso ("less motion") drops to a slower tempo immediately, and più mosso ("more motion") jumps to a faster one. The word subito, meaning "suddenly," is sometimes added to stress that the change is instant rather than eased into. These abrupt shifts carve a piece into contrasting sections and give the ear a clear signal that something new has begun. Because they are discrete jumps, they are easier to execute together than a gradual curve, but they still demand a shared internal reference so the whole group lands on the new speed at the same instant.

Metric modulation, briefly

The most precise tempo change is metric modulation, also called tempo modulation, a technique associated with the composer Elliott Carter. Here the new tempo is not chosen loosely but derived exactly from the old one: a specific note value in the first tempo is set equal to a different note value in the second, so a subdivision becomes the new beat. The effect is a seamless, mathematically exact gear change, and it is closely related to the way one groove can flip into half-time or double-time by promoting or demoting a metric level. Metric modulation is common in twentieth-century concert music and in progressive rock, wherever a composer wants the tempo to shift by an audible, proportional relationship rather than by feel.

Tempo-change terms at a glance

These Italian terms are the vocabulary you will meet in a score. Here they are side by side, with what each one does and where it typically turns up.

For the fixed speeds these changes move between, the tempo markings chart from Largo to Presto gives the reference points in BPM.

Intended change versus unintended drift

Everything above is deliberate. That is the crucial line to hold. When a piece slows into a cadence or a pianist bends a phrase with rubato, the timing is chosen, structured and repeatable, and the whole ensemble shares the plan. That is very different from rushing and dragging, the unintended creep in tempo that happens when a player speeds up in an exciting passage or lags in a hard one without meaning to. Drift of that kind is usually unwanted, tends to be inconsistent from take to take, and pulls players apart rather than moving them together.

The honest caveat is that the two can look similar on a graph, since both are simply the tempo changing over time. What tells them apart is intent and structure, not the raw fact of change. A deliberate ritardando has a shape a performer can reproduce and a purpose the listener can feel; accidental dragging is closer to noise. This is also why the core skill under both is the same: an accurate internal clock, so that when you speed up or slow down it is because you decided to. Our guide to keeping a steady tempo covers the practice side of building that reference.

Keep reading

• Rhythm vs tempo: what actually changes when the tempo moves, versus the rhythm on the page.
• Tempo markings chart: Largo to Presto: the fixed speeds a tempo change moves between, in BPM.
• Rushing and dragging: the unintended drift that a deliberate tempo change is not.

Sources: Grove Music Online (Oxford University Press), "Tempo" and "Rubato"; Open Music Theory, chapters on tempo and expression; Bruno H. Repp, "A microcosm of musical expression: I. Quantitative analysis of pianists' timing in the initial measures of Chopin's Etude in E major," Journal of the Acoustical Society of America 104 (1998): 1085–1100; Richard Hudson, Stolen Time: The History of Tempo Rubato (Oxford University Press, 1994).