MUSIC: MAD ABOUT MAHLER

It's easy to dismiss Gilbert Kaplan as just another rich New Yorker with a hobby he can afford. Kaplan, 55, former publisher of Institutional Investor magazine, is mad for Mahler. Through his private Kaplan Foundation, formed a decade ago, he has immersed himself in the composer's life and music, tracking down every extant photograph of Mahler for a book and issuing a facsimile of Mahler's score of the Symphony No. 2, better known as the "Resurrection" Symphony--which just happens to be the object of Kaplan's special passion.

For Kaplan's Mahler fixation extends to actually stepping up on a podium and conducting...