Complex sentence: Starting in 1954 during Steve Allen's tenure as host of NBC-TV's "Tonight", Doc Severinsen played first trumpet in the band directed by Skitch Henderson, several months before Johnny Carson's becoming host in October 1962.
Split into simpler sentences: Starting in 1954 during Steve Allen's tenure as host of NBC-TV's "Tonight", Doc Severinsen played first trumpet in the band directed by Skitch Henderson. He actually joined "The Tonight Show Band" several months before Johnny Carson's becoming host in October 1962.