Complex sentence: Trevor Horn, who was a major factor in the success of Yes's previous disc "90125" was part of the early recording sessions, but dropped out after a few months due in major part to his inability to get along with keyboardist Tony Kaye.
Split into simpler sentences: Trevor Horn, who was a major factor in the success of Yes' previous disc "90125", was part of the early recording sessions. However, he dropped out after a few months due in major part to his inability to get along with keyboardist Tony Kaye.