The roughly synonymous phrase a bene placito ('in accordance with [one's] good pleasure') is less common but, in its Italian form a piacere, has entered the musical lingua franca (see below).
Baroque music, especially, has a written or implied ad libitum, with most composers intimating the freedom the performer and conductor have.
"Ad-lib" is used to describe individual moments during live theatre when an actor speaks through their character using words not found in the play's text.
When performing as Colombo, Falk would ad-lib such mannerisms as absent-mindedness, fumbling through his pockets, or asking for a pencil, all in a deliberate attempt to frustrate his co-stars in the scene and obtain a more genuine reaction.
[4] The HBO sitcom Curb Your Enthusiasm by Seinfeld co-creator Larry David primarily uses retroscripting and ad lib instead of scripted dialogue.