I admit it: I was a teenage stereogeek. Remember wow and flutter? Signal-to-noise ratios? Rumble? I still have (and use) the Technics SA-5170 receiver I bought in 1979 at the Harmony Hut in the Willowbrook Mall in Wayne, N.J. It has a lovely, wide flywheel tuner and a lamp so bright I used to read by it. Since those days, stereo equipment has gotten so cheap and so near sonic perfection that gear-minded adolescents with a statistical bent have transferred their technofetishism to computers, where meaningful progress can and does still happen. In the meanwhile, though, Dr. Sidney Harman has taken what was a fairly small hi-fi manufacturer, Harmon Kardon, and parlayed it into a Fortune 500 company, Harman International Industries. Harman will be giving a lecture on the future of his industry, the contents of which one hopes will be less obvious than its title: “Who’s Listening? The Digital Revolution and Its Implications for Musicians and Audiences.” See if they get the sound right and bask in the wisdom of immense wealth at 7 p.m. at the Levine School of Music, 1690 36th St. NW. FREE. For reservations call (202) 337-2227. (James Lochart)