Complex sentence: His first job as a musician came in 1940 when he joined the Sam Donahue Orchestra, and then joined up with Red Norvo in 1941, later performing also with the bands of Stan Kenton and with Benny Goodman's bebop orchestra.
Split into simpler sentences: His first job as a musician came in 1940 when he joined the Sam Donahue Orchestra, and then joined up with Red Norvo in 1941. Bert has had a surprisingly active career in jazz, performing also with the bands of Stan Kenton and with Benny Goodman's bebop orchestra.