I have some geekass theories about music. I believe, for instance, that no band ever achieves greatness ’til it writes a song in 3/4, that Faith No More was secretly the most important band of the ’90s, and that the beat from “Not Fade Away” is the basis of 85 percent of all jam music. Daniel Levitin has a lot of theories about music, too, but he’s actually done research to back them up—he was a session musician, A&R rep, and label president before retiring to study audio recording and psychology in the ’90s. That would explain why the title of his book, This Is Your Brain on Music, is as dated as most of his musical references. Still, Levitin can entertain, whether explaining why humans respond to certain rhythms, timbres, and volumes or chasing down the provenance of the “Shave and a Haircut” rhythm. Find out why you suspect your iPod’s shuffle mode isn’t really random when Levitin speaks at 6:30 p.m. at the Freer Gallery of Art’s Meyer Auditorium, 12th St. and Independence Ave. SW. $25. (202) 357-3200. (Andrew Beaujon)