Complex sentence: Gabel was first associated with Orson Welles when he played Javert in his six-part radio adaptation of "Les Misérables" (1937), and he became one of the original members of Welles's Mercury Theatre repertory company.
Split into simpler sentences: Gabel was first associated with Orson Welles when he played Javert in his six-part radio adaptation of "Les Misérables" (1937). He became one of the original members of Welles's Mercury Theatre repertory company.