Pianist Leon Fleisher's tragedy was losing his right hand to a crippling muscle disorder. His triumph was showing the world that it hardly mattered. After building a new life for himself in the past quarter-century as a conductor and teacher, Fleisher, 62, returned to the concert stage last weekend for a bravura piano recital featuring solo works for the left hand only. His homecoming performance in the Kennedy Center's crowded Terrace Theater was praised by music critics with the same enthusiasm that greeted his Carnegie Hall debut with the New York Philharmonic in 1944, when he was a gangly 16-year-old from San Francisco. Several works on Saturday night's program were written for other great pianists who, like Fleisher, were unable to use their right hands. They included Russian composer Alexander Scriabin, who suffered the same ailment as Fleisher, and Viennese pianist Paul Wittgenstein, who lost his right arm in World War I. It was Fleisher's first solo recital in a major concert hall since he was stricken more than 25 years ago. When Fleisher withdrew from the concert stage in April 1965, on the eve of a European tour with the Cleveland Orchestra, his right-hand fingers had become weak, numb and beyond control. Once hailed by The New York Times as ``the finest American pianist of his (and probably any) time,'' Fleisher was devastated. ``I had the sense that my whole world had dropped out from under me,'' he said. ``My whole life's direction pointed toward the abyss. For two years, I struggled with, `Why did this happen to me?' I was wallowing in self-pity.'' He was rescued by Dina Koston, a former student at the Peabody Institute in Baltimore, who persuaded him to become co-director and conductor of the Kennedy Center's resident chamber music ensemble, the Theater Chamber Players, in 1968. ``She came up with a suggestion that took me out of that abyss and showed me I could still function as a musician,'' Fleisher said. Thus began his resurrection as guest conductor of many of the world's major symphony orchestras, an opera conductor, associate conductor of the Baltimore Symphony and artistic director of the Berkshire Music Center at Tanglewood, Mass. Meanwhile, Fleisher completed 30 years of teaching at Peabody last spring, and is busy recording the known repertoire of left-hand piano concertos with the Boston Symphony. He plans to write his memoirs under the title, ``Eighty-Eight Keys And No Lock.'' Doctors have never diagnosed his affliction, which he dismisses as ``writer's cramp.'' A subsequent bout of carpal tunnel syndrome, a painful nerve disorder of the wrist and hand which Scriabin and Robert Schumann also suffered, was cured surgically. These ailments are common to professional pianists, typists and others whose work requires sustained, repetitive wrist motions. ``Man was not created for the computer keyboard or the piano,'' Fleisher said. Fleisher said he practiced ``incorrectly, even stupidly,'' for six to eight hours a day for 20 years until the muscles of his right hand ``just curled up and said, don't beat on me anymore.'' The damage was irreversible. No matter. Fleisher is too busy savoring his rich new life to waste time fretting over the past. ``I've learned a lot,'' he said. ``What you think are the most important things in the world are not the most important. What's important are relations with people, nature, the world around us. That's where it's at.'' Fleisher said his handicap has ``somehow opened my ears,'' making him a good listener for the first time in his life. He believes it also has improved his teaching by forcing him to verbalize his musical concepts, instead of demonstrating them on the keyboard. The ecstasy of conducting has been a revelation, he said. He recalled conducting the Boston Symphony in a performance of Rachmaninoff's Symphony No. 2. ``It took my breath away,'' he said. ``It was like riding the crest of a tidal wave. It was incredible.'' He also enjoyed ``some extraordinary moments'' conducting a community orchestra in Annapolis, Md., whose amateur musicians ``got so caught up that they rose to levels they never knew they were capable of.'' Just as he has finally learned to play the piano properly, using forearms and shoulders rather than hammering away with curled fingers, Fleisher has become aware of the hazards of such ordinary objects as doorknobs. ``It's a totally unhealthy design,'' he said, curving his fingers around an imaginary doorknob and twisting his wrist. ``Door handles are much better.''