One of the great strengths of the Warbler Guide is its innovative information on sounds. One of the great weaknesses of books in general is they don't play MP3s! For less than $5 you can solve that problem by purchasing the Song and Call Companion, which has every song, call, and example in the book in MP3 form. Play along as you read (they're in book order!), use them to quiz yourself, make playlists for study, or to remind yourself of what you've learned! They will work on any phone, computer or e-device that can play songs.