Complex sentence: Eileen Joyce, whose name does not appear in the credits, was the pianist who substituted for Todd on the soundtrack, and also made a short film for Ann Todd to practise to, and even coached Todd personally in her arm movements.
Split into simpler sentences: Eileen Joyce, whose name does not appear in the credits, was the pianist who substituted for Todd on the soundtrack. She also made a short film for Todd to practise to, and even coached Todd personally in her arm movements.