The first time you play a C#dim7—such as the one in Ex. 1a—you may find yourself wondering why you’d ever need such a dissonant cluster of notes. Truth is, diminished 7s and other such strident grips are, ironically, incredibly useful for making progressions sound smoother. Plug that C#dim7 between C and Dm7 (Ex. 1b), and its jagged shape all but disappears—like the last piece of a jigsaw puzzle. Get hip to its pungent sound; you’ll start hearing it everywhere —not just in jazz, but also in rock, soul, blues, and other genres. This lesson includes Power Tab and is featured on the following CD compilations: JAZZ U, ACOUSTIC U. Get more audio and video lessons, notation and tab at TrueFire TV (http://truefiretv.com)