Complex sentence: He is probably best known for playing the lead role of the Baker in the original Broadway production of "Into the Woods" by Stephen Sondheim; his first major role, though, was Marvin in William Finn's first musical, "In Trousers".
Split into simpler sentences: He is probably best known for playing the lead role of the Baker in the original Broadway production of "Into the Woods" by Stephen Sondheim. His first major role was Marvin in William Finn's first musical, "In Trousers".