Check out this story from Arizona State University's ASU News, all about an upcoming performance of Eric Mandat's Double Life by ASU professor Robert Spring. The piece is dedicated to William O. Smith, and in an homage to his "double life" as a jazz musician and composer of modern classical music, the first movement calls for the unusual effect of playing two clarinets at once. The B-flat clarinet is given jazzy licks and the A clarinet performs "serious" material with multiphonics. The second movement is written for a clarinet with PVC pipe extension, allowing three new low notes to be played with the legs. In the ASU article, Spring discusses the challenges of practicing this unusual piece.
Below is a video which was included with the ASU article, featuring Robert Spring performing the first two movements of Double Life.