Asked about which aspect of his work gives him the most satisfaction, Lang ponders for a moment and concludes: "It would be easiest for me to say that my biggest thrill is to see an idea of mine become a three dimensional reality, especially if it may be a $50 million project. But actually, an even bigger thrill for me is to go to an obscure place in the world, and see a bit of improvement in people's lives through the effort of someone who was my former disciple." ******** WESTSIDER RUTH LAREDO Leading American pianist 12-30-78 She has frequently been called America's greatest female pianist -- a title which, as recently as the 1960s, almost any woman would have coveted. But when the year is 1978 and the musician is Ruth Laredo, this "compliment" brings a different response. "I have mixed feelings about it," says Miss Laredo, sitting back on the couch of her West Side living room. "I would really rather be known as an American pianist. Being female doesn't preclude playing some of the most powerful sounds on the piano." Her words are backed by accomplishments. In October, Ruth came to the end of a four-year project to record the complete works for solo piano by Sergei Rachmaninoff, the late Russian-born composer who emigrated to the U.S. after the Revolution of 1917. Almost all of his piano works were composed before 1910, and they rank among the most technically difficult pieces ever written for the instrument. Laredo is the first person in history to record the piano solos in their entirety. Columbia Records will release the final three discs of the seven-album set in early 1979. Slender, graceful, and radiantly attractive, Laredo is still adjusting to her recently acquired status as a major international artist. For 14 years she was married to the acclaimed Bolivian-born violinist, Jaime Laredo, and during most of that time she was known primarily as his accompanist. Shortly after their marriage broke up in 1974, her career began to soar. That year the first of her Rachmaninoff recordings was made, and it won rave reviews. Her Lincoln Center debut with the New York Philharmonic Orchestra in December 1974 caused such a sensation that she was quickly signed up to perform with the Boston, Philadelphia, National Symphony, Cleveland, and Detroit orchestras. "After 15 years," recalls Ruth, "I was an overnight success." Now, at 41 -- but looking considerably younger -- she can look back on four years of unbroken triumph. Following a recital at Alice Tully Hall in 1976, the _New York Times_ reported that she "operated within a relatively narrow range -- from first-rate to superb." Her talents have been constantly in demand ever since across the U.S. and Canada. During the 1976-77 season she had over 40 concerts, including tours of Europe and Japan. This season she will perform in Japan and Hong Kong.