This riff has a traditional blues shuffle feel, but includes offbeat chord stabs to unsettle the groove. Use downstrokes for the shuffle and lightly palm-mute to add clarity to the rhythm. For the offbeat chord stabs use upstrokes, a decent amount of attack, and let the notes ring. This adds more surprise when the parts break away from the traditional groove. The riff ends with a chromatic phrase, which is doubled on the bass. Use downstrokes for the whole sequence and relax your fretting fingers between each note. This adds separation to every note of the end phrase.
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