Final answer:
The jazz style that often featured a piano-less ensemble and contrapuntal improvisations is bebop.
Step-by-step explanation:
The jazz style that often featured a mixed-timbre, piano-less ensemble as well as contrapuntal improvisations is bebop.
Bebop emerged in the 1940s as a response to the commercialization and simplification of jazz. It featured small ensembles with a focus on individual improvisation, complex harmonies, and fast tempos.
Contrapuntal improvisations in bebop refer to the practice of multiple musicians improvising simultaneously in a contrapuntal or polyphonic manner, creating intricate musical interactions.
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