I READ ABOUT THIS BEAUTIFUL CONCERT GRAND PIANO being donated to the Cadillac Hotel, one of  many single-room resident hotels in San Francisco's Tenderloin. Although comedian Dave Chappelle rightfully says, "There's nothing tender" about the neighborhood, it is filled with a lot of good people who years ago could walk just steps to hear great jazz at clubs like the Black Hawk, a frequent stop for Thelonious Monk and Miles Davis.     Concert grands are pretty special and I thought it would be great to play at the Cadillac. I got the chance Sept. 28. It was a momentous occasion. The piano played and sounded incredible. People could hear every note. I felt like I was performing at Carnegie Hall. You're listening to me live at the Cadillac playing Duke Ellington's "Sentimental Mood," Ellington/Billy Strayhorn's "Satin Doll" and Don Pullen's "Bonney's Bossa Nova."