Here's a laid-back blues by Wes Montgomery. Nothing exceptionally tricky here except for measures 9 and 10 of each chorus. I a regular blues in Eb, those chords would be V and IV, i.e. Bb7 and Ab7. Instead, Montgomery shifts the chords up. Measure 9 is F#m7, B7, or 1/2 step above the usual Bb7 chord. There are a bunch of tonalities in measure 10, but they converge around the IV chord (Ab13) eventually. So just make sure you play measure 9 a half-step higher than you might have planned in a regular blues.