Ninebuzz Software LLC has Guitar Jam Tracks: Acoustic Blues (iTunes Link) in the iTunes App Store for FREE for a limited time.

Guitar Jam Tracks: Acoustic Blues makes the guitar fun. Practice jamming, learning scales and soloing to a blues jam track in keys A, B, C, D, E, F and G right from your iPhone! Our easy-to-read scale charts show you exactly where to put your fingers to start sounding like a pro. See for yourself why thousands of guitarists love this app!