(Willis). Each book in this series contains short warm-up exercises to be played at the beginning of the student''s practice session. Performing these technical exercises will help develop strong hands and flexible fingers. This book includes access to audio files online. The audio is accessed online using the unique code inside each book and can be streamed or downloaded. The audio files include PLAYBACK+, a multi-functional audio player that allows you to slow down audio without changing pitch, set loop points, change keys, and pan left or right.