The Real Book you know and love has now been updated to include backing tracks for 240 songs available online for download or streaming! The four play-along CDs sold separately for $25 each so this is an amazing package price! The audio is accessed online using the unique code inside each sleeve 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.