LENA HORNE, BACK ON STAGE

Jurassic, schmassic-Lena Horne's June 20th concert at New York's Avery Fisher Hall really defied the laws of nature. Virtually retired from performing for seven years now, Horne seemed frail and lost at the Oscars. Then this, the impossible: In a performance that was not just focused but driven and defiant, not just strong but dominating, Horne did a 40-minute-long set of tricky Billy Strayhorn songs (most of which she hasn't sung in more than 30 years) with breathtaking passion. At 75, she outsang any three 25-year-olds combined. (Horne turned 76 on June 30.) Done in rare tribute to Strayhorn-the late composer Horne calls her ''soul mate''-this show, part of the JVC Jazz Festival, might seem just like the work of a pro. It was, however, clearly an act of love.