Sheets of sound was a term coined in 1958 by DownBeat magazine jazz critic Ira Gitler to describe the new, unique improvisational style of John Coltrane.
[4][6] Coltrane used the "sheets of sound" lines to liquidise and loosen the strict chords, modes, and harmonies of hard bop, whilst still adhering to them (at this stage in his musical development).
[7] Playing with the Miles Davis groups, in particular, gave Coltrane the free musical space in which to apply harmonic ideas to stacked chords and substitutions.
[7] Concepts of vertical (chordal) versus horizontal (melody) are key ideas in the work of George Russell, whom Coltrane had recorded with in September 1958.
[6] In "Trane on the Track", an article published on October 16, 1958 in DownBeat magazine, Coltrane spoke to Ira Gitler about the sheets of sound, telling him, "Now it is not a thing of beauty, and the only way it would be justified is if it becomes that.