TAR, 12/11, METRO Over the years Tar's hard riff-driven music has gotten almost impossibly distilled. John Mohr and Mark Zablocki's airtight interlocking guitar patterns merge with the taut, almost martial rhythms of drummer Mike Greenlees and the brittle, drilling bass lines of Tom Zaluckyj with minute, anal precision. It's propulsive and audacious in its unflinching discipline, but then again, a machine doesn't move you. These locals play a split bill with flimsy Japanese pop punkers Shonen Knife. ALEJANDRO ESCOVEDO, 12/11, SCHUBAS On his recent release Thirteen Years the Austin-based singer-songwriter makes a startling shift from the contemplative roots rock of his 1992 solo debut, Gravity. The bittersweet softness of the dark string arrangements and the sudden emphasis on ballads might be explained, sadly, by the suicide of his estranged wife, yet Escovedo's wrenching metaphors and his poetic evocations of loss convey a powerful universality. In particular, the achingly gorgeous "Baby's Got New Plans" portrays painful resignation with a loaded shrug of the shoulders: "The grand mistake was all it took / To burn away the flame / And cast a shadow on everything / That came before that day." The music's innate emotionality and tenderness match the songs' subjects perfectly, yet overall the tone remains hopeful. Escovedo's known for mixing up musical settings, from playing solo to using a modified "orchestra," and for this performance his acoustic guitar will be fleshed out with a cello and the violin of Poi Dog Pondering's Susan Voelz. FLOP, 12/11, LOUNGE AX This Seattle four-piece harbors an unabashed love for 70s power pop, but to these ears the new album, Whenever You're Ready, sounds like cut-rate Fastbacks (with whom singer-guitarist Rusty Willoughby once served a brief stint), not punky or poppy enough to make you shake a tail feather. They open for the always excellent and newly cocky Red Red Meat, whose Sub Pop debut album is due out next month. SOULS OF MISCHIEF, 12/12, CHINA CLUB This Oakland quartet pairs the heavy double-bass jazz samples favored by headliners A Tribe Called Quest with the pinched but rhythmically quirky rap style of Das EFX (without the relentlessly forced Jamaican patois). It ain't revolutionary, but it works. De La Soul also appear. FACE THE MUSIC, 12/12, HOTHOUSE The new-music series curated by composer/improviser Gene Coleman continues with two programs; the first, at 8, is dedicated to "Sound Art," and includes a collaborative effort by Reader staffer Renaldo Migaldi and instrument inventor Hal Rammel. The second show, at 9:30, matches bass clarinetist Coleman with three guitar-playing free improvisers, John Corbett, Gastr del Sol's David Grubbs, and Flying Luttenbacher's Dylan Posa. US3, 12/15, PARK WEST Digable Planets and A Tribe Called Quest have proved that fusions of hip-hop and jazz can work when the jazz element is confined to rhythm and riff samples. When the two styles are given a more equitable weight, as in acid jazz, the merger turns to mush. Bring in "real" jazz mercenaries and you're in really big trouble. Witness the disaster of Guru's schlocky meeting with Donald Byrd and Branford Marsalis, or talented jazz saxophonist Greg Osby's hokey crossover try. Britain's US3 are delving into similar territory and arriving at similar mediocrity. On their debut, Hand on the Torch, a legitimate saxophonist like Steve Williamson is reduced to inconsequential horn loops, and rhythmic hardness or inventiveness is weakened by a generally nonfiery vibe. The album art is nice, though.