Lead sheet

A lead sheet is a form of musical notation that specifies the essential elements of a popular song: the melody, lyrics and harmony. The melody is written in modern Western music notation, the lyric is written as text below the staff and the harmony is specified with chord symbols above the staff.

The lead sheet does not describe the chord voicings, voice leading, bass line or other aspects of the accompaniment. These are specified later by an arranger or improvised by a performer or rhythm section, and are considered aspects of the arrangement or performance of a song, rather than a part of the song itself. An exception occurs in some cases in a fake book, when a song has an ostinato bass part which forms an essential part of the song's identity, such as the bassline in "A Night in Tunisia"; in these rare cases, a few bars of the bassline may be given.

A lead sheet is often the only form of written music used by a small jazz ensemble. One or more musicians will play the melody while the rest of the group improvises an appropriate accompaniment based on the chord progression given in the chord symbols, followed by an improvised solo also based on the chord progression. Similarly, a sufficiently skilled jazz pianist should be able to accompany a singer and perform a song by her or himself using only a lead sheet.

...
Wikipedia