Musical terminology in the context of "Glissando"

In musical terminology, tempo (Italian for 'time'; plural 'tempos', or tempi from the Italian plural), measured in beats per minute, is the speed or pace of a given composition, and is often also an indication of the composition's character or atmosphere. In classical music, tempo is typically indicated with an instruction at the start of a piece (often using conventional Italian terms) and, if a specific metrical pace is desired, is usually measured in beats per minute (bpm or BPM). In modern classical compositions, a "metronome mark" in beats per minute, indicating only measured speed and not any form of expression, may supplement or replace the normal tempo marking, while in modern genres like electronic dance music, tempo will typically simply be stated in bpm.

Tempo (the underlying pulse of the music) is one of the three factors that give a piece of music its texture. The others are meter, which is indicated by a time signature, and articulation, which determines how each note is sounded and how notes are grouped into larger units. While the ability to hold a steady tempo is a vital skill for a musical performer, tempo is malleable. Depending on the genre of a piece of music and the performers' interpretation, a piece may be played with slight variations in tempo, known as tempo rubato, or significant variations. In ensembles, the tempo is often maintained by having players synchronise with a conductor or with a specific instrumentalist, for instance the first violin or the drummer.

Tempo rubato (Italian for 'stolen time'; UK: /ˈtɛmpoʊ rʊˈbɑːtoʊ/, US: /ruː-/, Italian: [ˈtɛmpo ruˈbaːto];) is a musical term referring to expressive and rhythmic freedom by a slight speeding up and then slowing down of the tempo of a piece at the discretion of the soloist or the conductor. Rubato is an expressive shaping of music that is a part of phrasing.

While rubato is often loosely taken to mean playing with expressive and rhythmic freedom, it was traditionally used specifically in the context of expression as speeding up and then slowing down the tempo. In the past, expressive and free playing (beyond only rubato) was often associated with the terms "ad libitum". Rubato, even when not notated, is often used liberally by musicians, e.g. singers frequently use it intuitively to let the tempo of the melody expressively shift slightly and freely above that of the accompaniment. This intuitive shifting leads to rubato's main effect: making music sound expressive and natural. Nineteenth century composer-pianist Frédéric Chopin is often mentioned in the context of rubato (see Chopin's technique and performance style and his adaptation of the bel canto idiom).