With these backing blues tracks, you can learn how to play the alto saxophone blues. The play along blues tracks for alto sax will help you develop a feel the blues changes over time.  The chords for this alto saxophone blues track are:
In the 12 Bar Blues, the 1 Chord is ‘G Chord’ - Notes G, B, D
In the 12 Bar Blues, the 4 Chord is ‘C Chord’ - Notes C, E, G
In the 12 Bar Blues, the 5 Chord is ‘D Chord’ - Notes D, F#, A
Some MAGIC notes to play around with are E, G, A