Ad libitum is Latin for "at one's pleasure"; it is often shortened to "ad lib" (as an adjective or adverb) or "ad-lib" (as a verb or noun). The roughly synonymous phrase a bene placito ("at [one's] good pleasure") is less common but, in its Italian form a piacere, entered the musical lingua franca (see below).

Music or rhythm

As a direction in sheet music, ad libitum indicates that the performer or conductor has one of a variety of types of discretion with respect to a given passage:

• to play the passage in free time rather than in strict or "metronomic" tempo (a practice known as rubato when not expressly indicated by the composer);
• to improvise a melodic line fitting the general structure prescribed by the passage's written notes or chords;
• to omit an instrument part, such as a nonessential accompaniment, for the duration of the passage; or
• in the phrase "repeat ad libitum," to play the passage an arbitrary number of times (cf. vamp).

Note that the direction a piacere (see above) has a more restricted meaning, generally referring to only the first two types of discretion. Baroque music, especially, has a written or implied ad libitum, with most composers intimating the freedom the performer and conductor have.

For post-Baroque classical music and jazz, see cadenza.

References

• Ehrlich, Eugene (1985). Amo, Amas, Amat and More. New York: Harper & Row, Publishers. p. 23.