Semisonic will play its first show in two years Oct. 8 at First Avenue, for a cause close to the band: Sound engineer Brad Kern, their longtime right-hand-man, was in a hit-and-run bike accident last month. He is expected to fully recover, but of course his medical bills are outrageous, plus he has been out of work. Not only is Semisonic playing the gig, dubbed Brad's Benefit, but Mason Jennings, the Twilight Hours and Two Harbors have also lined up to play it and another late-'90s/early-'00s band will be making a much-welcome reunion, the Hang-Ups. Tickets ($22.50) will go on sale Aug. 20 at noon.