Fletcher Henderson's bassist John Kirby in 1930 revolutionized the rhythm
section of jazz.
The epitome of chamber jazz in the swing era was the sextet (Charlie Shavers on trumpet, two reeds, Billy Kyle on piano, bass and drums) formed by Kirby after
leaving Henderson. Their emphasis on
intricate arrangements, clockwork craftmanship and introverted moods contrasted
with the prevailing habits of the big-band era and predated cool jazz.
Notwithstanding the success of Shavers's Undecided (october 1938),
most of their repertoire was borrowed from classical music.