God help whoever tries to write a history of experimental music in Seattle. Anyone so foolhardy faces three challenges: tallying dozens of individual artists in the scene; assessing the influence (if any) of those who move here and stay for just a year or two; and, most perplexingly, tabulating all the musicians and groups continually emerging from various collectives, including the decade-old Monktail Creative Music Concern (MCMC).

With almost two dozen side projects, one-off ensembles, and regularly gigging groups, the Monktailers defy categorization. The band names, which range from ominous (Special O.P.S., Rusty Nail) to whimsical (Johnny and the Primordial Poo remains my favorite) to enigmatic and witty (Reptet, Non Grata, Deal's Number), aren't much help.

Several years ago while I was researching an aborted book on experimental music in Seattle, Monktail cofounder John Seman explained why the collective has spawned so many groups: "The folks involved get together under different aliases contingent on their predilection within any situation that permits them to exist. Groups generally range from 2 to 10 players and have free improvisation/spontaneous composition as their underlying principle. These specialized ensembles present the group members with the unique opportunity to improvise in many different contexts—a performance of one particular unit organically mutates into another, offering the listener the unparalleled, or at least amusing, experience of live, acoustic, sonic gymnastic hallucinations. It's a gas."

This weekend, MCMC celebrates a decade in Seattle with "The Dangerous Petting Zoo" (Fri Dec 11, the Mix, 6012 12th Ave S, 8 pm, $6), a sly riff on the kid-friendly "instrument petting zoos" that have become a staple of classical chamber groups. Here, the Monktailers offer a lineup including Figeater, Shit Orange Horsey (a fun "dada-inspired, free metal group" with four singers, guitars, and accordion), the parlor-folk songs of Goatgirl, and Bird May Bite (the solo moniker for Monktail accordionist Scott Adams). Led by clarinetist Beth Fleenor, Figeater make improvised music that ranges from insistently propulsive and buoyant—Fleenor can channel the spirit of Raymond Scott with aplomb—to aloof atmospheres, thugged-up backbeats, and loony, melismatic rants.

Finally, don't miss the Esoterics (Sat Dec 12, St. Joseph's, 732 18th Ave E, 8 pm, and Sun Dec 13, Holy Rosary, 4139 42nd Ave SW, 3 pm, $15–$20). Instead of serving up the usual holiday blather—I can spastically croon "Sleigh Ride" all by myself, thank you very much—this a cappella ensemble sings Alfred Schnittke's "Concerto for Mixed Choir," a masterly synthesis of liturgical chant and elements of contemporary composition; keep your ears open for hovering drones and fleeting moments of remote, eerie dissonance. Also on the program: John Joubert's "Sleep Canticle" and the famed "Deutsche Motette" of Richard Strauss. recommended