For those who bow at the altar of the groove, the Bumps project offers some kind of polyrhythmic communion. John McEntire, John Herndon, and Dan Bitney, drummers for the post-rock outfit Tortoise, do nothing but groove on this offshoot, which crams 23 tracks into just over 30 minutes. Each track runs somewhere between 19 seconds and two minutes, and, despite the implications of titles like “Sniper Growl” and “Don’t Cry, My Son”, consists of little more than a wiry drum kit kicking out a unaccompanied jam. The drum patterns range from frenetic to laidback; the performances are like rubber bands one minute and slackened ropes the next. Rarely, as on “Tryplmeade Gorsmatch”, other percussive timbre is tossed into the mix, but Bumps is primarily a succession of skeletal drum pieces. Seriously groovy, yes, but what’s the point? Loop fodder? Preludes to a breakbeat? A home for orphaned rhythms? Bumps may make you move, but getting it to really move you may prove to be something of a challenge.