In 2013, over a quarter century removed from his first album, Joe Satriani uses his solo albums as a way to stretch himself, both to flaunt his skills and perhaps to move him into areas where he's not quite comfortable. Unstoppable Momentum, his first album since 2010's boogie- and prog-heavy Black Swans & Wormhole Wizards, finds the guitarist occasionally indulging himself in a bit of swing, letting him ride an elastic beat ("Three Sheets to the Wind" has a supremely delicate touch), and he also digs into a bit of a nasty ZZ Top groove on "Jumpin' In," a boogie he turns inside-out on its immediate successor "Jumpin' Out." This is a pretty good indication that this is the work of a virtuoso who enjoys playing with his surroundings, tweaking tempos and arrangements to coax out unexpected wrinkles…