A ricercar (also spelled ricercare, Italian pronunciation: [ritʃɛr'kare]) is a type of late Renaissance and mostly early Baroque instrumental composition. The term ricercar means to search out, and many ricercars serve a preludial function to "search out" the key or mode of a following piece. A ricercar may explore the permutations of a given motif, and in that regard may follow the piece used as illustration. The term is also used to designate an etude or study that explores a technical device in playing an instrument, or singing.
In its most common contemporary usage, it refers to an early kind of fugue, particularly one of a serious character in which the subject uses long note values. However, the term has a considerably more varied historical usage.
In the sixteenth century, the word ricercar could refer to several types of compositions. Terminology was flexible, even lax then: whether a composer called an instrumental piece a toccata, a canzona, a fantasia, or a ricercar was clearly not a matter of strict taxonomy but a rather arbitrary decision. Yet ricercars fall into two general types: a predominantly homophonic piece, with occasional runs and passagework, not unlike a toccata, found from the late fifteenth to the mid-sixteenth century, after which time this type of piece came to be called a toccata; and from the second half of the sixteenth century onward, a sectional work in which each section begins imitatively, usually in a variation form. The second type of ricercar, the imitative, contrapuntal type, was to prove the more important historically, and eventually developed into the fugue. Marco Dall'Aquila (c.1480–after 1538) was known for polyphonic ricercars.