The music of the Bad Plus, the Coen Brothers of jazz, has always been a Dali-esque calculus of melting equations, surrealistic geometry, trigonometric absurdity, and algebraic conundrums, and their latest earthshaking news is a matter of basic mathematics. Following a year-ending, week-long run at NYC’s Village Vanguard, the BP will subtract pianist Ethan Iverson and add Orrin Evans, making the trio’s annual holiday run at the Dakota the original lineup’s penultimate residency and their final gigs in the heart of their Twin Cities/western Wisconsin roots. Iverson’s plans aren’t specific, but lately he’s played with a Monk-oriented trio, continues to be a busy critical voice online, and will launch a new, NYC jazz-oriented site. Evans, a brilliant Philly-based pianist with equally far-reaching, eclectic influences, has been in the studio this fall with drummer Dave King and bassist Reid Anderson working on new BP material. They pledge to continue playing the band’s extensive songbook live, including the radically deconstructed pop, rock, and country tunes that have made the Plus iconic iconoclasts. Meanwhile, Iverson’s local swan song should be a honking treat.