While not music-specific, we have a couple of events here in Minneapolis that just might provide you with access to your target audience:
Minnesota CONvergence
July 1-4, 2010
Sheraton Bloomington Hotel
http://www.convergence-con.org
From the CONvergence FAQ:
"CONvergence is a convention for fans of Science Fiction and Fantasy in all media, and is held at the Sheraton Bloomington Hotel in the Twin Cities area of Minnesota on the first full weekend of July each year. CONvergence is a production of The Minnesota Society for Interest in Science Fiction and Fantasy, a 501(c)3 non-profit organization, and acts as an annual fundraiser for that organization.
CONvergence features four days of nearly round-the-clock entertainment including: Local and National Guests, Two Full Floors of Cabana Room Parties, Panels and other Programming, Live Music and DJ Dance, Costume Contest/Masquerade, Cinema Rex Movie Room, Theater Nippon Anime Room, Dealers Room, Art Show and Auction, ConSuite, COF2E2 Free Coffee Shop, Harmonic CONvergence, Connie's Space Lounge, Silent Auction, and more!"
Goth Prom
May 17, 2010
The Saloon (Downtown Minneapolis)
http://www.myspace.com/gothprom
From City Pages:
"No matter what your gothic persuasion (or lack thereof), the Saloon's Goth Prom makes for an excellent party. If you're goth already, you'll feel right at home amid pounding industrial music and a sea of black eyeliner and pleather. If you're a "normal" by nature, you're still more than welcome; just don a little black, put on enough white makeup to render your visage pallid, and blend into one of the more visually interesting crowds in Minneapolis. Last year's theme was Steampunk, that delightful mix of sci-fi and Victorian sensibilities, with head-turning sights like shoulder-perched animatronic ravens, goggles, and lace-lined corsets. This year, the theme encompasses the alchemical elements of fire, air, water, and earth, hinting that the celebrants may be more colorfully arrayed than in previous years. With door prizes, drink specials, and live DJs, it has all the makings of a fun time even without the eye candy. There's no cover for the event, but a nonperishable food donation is requested; it'll go to a deserving food shelf. 18+. "
- Heretic