I use these books and CDs to help with my intonation. They are fabulous. You learn what the song is supposed to sound like, you learn what good intonation sounds like, and you learn what good tone sounds like. You can play along with the cello track, and / or just the accompaniment track. You learn what the markings mean, to take repeats, to keep the tempo, and to employ the dynamics. Some tracks are easily recognizable, some not so much, but all will add to one's musical foundation / background. Highly recommended.