Art Ensemble of Chicago founder Roscoe Mitchell’s 1966 debut album was more than a set of music; it was an artistic manifesto. He was exploring the interaction not just between instruments, but between sound and silence. The members of the ensemble — Mitchell on alto sax, clarinet, flute, and recorder; Lester Bowie on trumpet, flugelhorn, and harmonica; Kalaparusha Maurice McIntyre on tenor sax; Lester Lashley on trombone and cello; Malachi Favors on bass; and Alvin Fielder on percussion — throw ideas back and forth, occasionally responding to one another but more often playing in carefully arranged unison. There are many moments on “The Little Suite” which prefigure what the Art Ensemble would be doing in 1969, but “Sound” itself is even more radical, with long passages of quiet, a single horn playing far outside its normal range with delicate, even cautious percussion providing subtle commentary. A genuinely unprecedented and pathbreaking album.