‘Jeru’ by Gerry Mulligan, recorded in 1949, is included in the classic 1957 compilation ’Birth of the Cool’. The band structure for this compilation (a nine piece band or ‘Nonet’) was inspired by a short lived group lead by Claude Thornhill.
Gerry Mulligan liked to incorporate polyphonic movement into his compositions – the supporting voices are always interesting. Very wise considering he was a baritone saxophone player!
Jazz has always been polyphonic – right from the traditional New Orleans stylings, right through to Ornette Coleman and beyond.
There is a wonderful collection of original Gerry Mulligan manuscripts at the Library of Congress web site (loc.gov)