A jam session is a musical act where musicians gather and play (or "jam") without extensive preparation or predefined arrangements. The art of singing and dancing in a prepared fictional play has been a time-honored tradition ranging to the early days of civilization. ... Wiktionary has a definition of: Act Act may refer to: in law, a written document that attests the legality of the transaction. ... A musician is a person who plays or composes music. ... In popular music an arrangement is a setting of a piece of music, which may have been composed by the arranger or by someone else. ...

The term jam can be more loosely used to refer to any particularly inspired or improvisational part of a musical performance, especially in rock and jazz music. Jam sessions, however, are generally for the benefit of the performers and not part of a public performance. Rock and roll (also spelled Rock n Roll, especially in its first decade), also called rock, is a form of popular music, usually featuring vocals (often with vocal harmony), electric guitars and a strong back beat; other instruments, such as the saxophone, are common in some styles. ... Jazz is a musical art form characterized by blue notes, syncopation, swing, call and response, polyrhythms, and improvisation. ...

Jam sessions are often used to develop new material, find suitable arrangements, or simply as a social gathering and communcal practice session. Jam sessions may be based upon existing songs or forms, may be loosely based on a chord progression or chart suggested by one participant, or may be wholly improvisational. Jam sessions can range from very loose gatherings of amatuers to sophisticated improvised recording sessions intended to be edited and released to the public. Liquid Tension Experiment, for example, produces albums from jam sessions. A chord progression (also chord sequence and harmonic progression), as its name implies, is a series of chords played in an order. ... Improvisation is the act of making something up as it is performed. ... Liquid Tension Experiment is an instrumental rock project consisting of Dream Theater members John Petrucci (guitar), Jordan Rudess (keyboard), and Mike Portnoy (drums), as well as progressive rock icon Tony Levin (bass, Chapman Stick) of King Crimson and Peter Gabriel. ... An album (from Latin albus white, blank, relating to a blank book in which something can be inserted) is a packaged collection of related things. ...

See also Jam band. The term jam band is commonly used to describe psychedelic rock-influenced bands whose concerts largely consist of bands reinterpreting their songs as springboards into extended improvisational pieces of music. ...