Complex sentence: Blackwell returned to music in the late 1950s and was first recorded in June 1958 by Colin C. Pomroy (those recordings were released as late as 1967 on the Collector label).
Split into simpler sentences: Blackwell returned to music in the late 1950s. He was recorded by Colin C. Pomroy in June 1958 (those recordings were released as late as 1967 on the Collector label).