William Savory

Part of what makes the Savory collection so alluring and historically important is its unusual format. At the time Savory was recording radio broadcasts for his own pleasure, which was before the introduction of tape, most studio performances were issued on 10-inch 78-r.p.m. shellac discs, which, with their limited capacity, could capture only about three minutes of music.

But Mr. Savory had access to 12- or even 16-inch discs, made of aluminum or acetate, and sometimes recorded at speeds of 33 1/3 r.p.m. That combination of bigger discs, slower speeds and more durable material allowed Mr. Savory to record longer performances in their entirety, including jam sessions at which musicians could stretch out and play extended solos that tested their creative mettle.

“Most of what exists from this era was done at home by young musicians or fans, and so you get really bad-sounding recordings,” Mr. Schoenberg said. “The difference with Bill Savory is that he was both a musician and a technical genius. You hear some of this stuff and you say, ‘This can’t be 70 years old.’ “

As a result, many of the broadcasts from nightclubs and ballrooms that Mr. Savory recorded contain more relaxed and free-flowing versions of hit songs originally recorded in the studio. One notable example is a stunning six-minute Coleman Hawkins performance of “Body and Soul” from the spring of 1940; in it this saxophonist plays a five-chorus solo even more adventurous than the renowned two-chorus foray on his original version of the song, recorded in the fall of 1939. By the last chorus, he has drifted into uncharted territory, playing in a modal style that would become popular only when Miles Davis recorded “Kind of Blue” in 1959.