Clarinetist Benny Goodman was one of the most popular bandleaders of the swing era, touring the country relentlessly and making hit records. But in the mid-1930s, he embarked on a side quest of sorts, forming a trio with pianist Teddy Wilson and drummer Gene Krupa that played short, precisely calibrated tunes with the intimacy of chamber music. Occasionally, they were joined by vocalist Helen Ward, whose vocal on “All My Life” has the maidenly quality of a woman who’s never even heard of the blues. When they cut loose, as on “Nobody’s Sweetheart,” the music is almost hyperactive, but it still holds together. After a year or so, they added vibraphonist Lionel Hampton to the ensemble, and created a startlingly beautiful sound: on a piece like “Vibraphone Blues,” Hampton’s lyrical ripples are shadowed by soft trills from Goodman, as Wilson and Krupa slip and slide together, swinging with impeccable gentility.