Watch the Common Tone online guitar lesson by Joe Dalton from 50 Acoustic Blues Licks You MUST Know
This is a jazzy sounding turnaround. The common tone is the 1st string open E. This is the note that links all of these chords and gives our ears the common sound to identify with. The chords are A9, G13, F#7, F maj7, and finally the tonic, E.
The tri-tone substitutions are C#7#9 in place of the G13. The top part of the chord stays, but the bass note moves a tri-tone (augmented fourth). The interval is 3 steps. The B7#9 is the substitution for the Fmaj7.