WHEN entertainer Michael Feinstein -- the rising young interpreter of Gershwin-era show tunes -- was a small child, his talent once got him in trouble. Toddling over to the family piano, he began to pick out ``Do-Re-Mi,'' a song from ``The Sound of Music'' he'd recently heard on the phonograph. ``When did your father teach you that?'' his mother asked Michael, who'd never played anything before. When he kept insisting he hadn't learned it from his father but was playing it by ear, his exasperated mother sent him to bed without supper -- until Dad came home and confirmed the tot's story.
Nobody hearing one of Mr. Feinstein's sparkling supper-club performances today will doubt that his early promise has been richly realized. Still playing and singing by ear, he presides at the keyboard like a blithe spirit of the '30s and '40s, deftly ushering in the music of that period with a grace and aplomb that not only have garnered raves in the United States, but have earned him a London debut to be made in July. His record and cassette ``Pure Gershwin'' (Parnassus label) -- a sleeper hit -- is steadily broadening his audience. ``Live at the Algonquin,'' a new record (and cassette) with an Al Hirschfeld caricature of Feinstein on the jacket, has just been released. Among his other dates, he performs next year in the Hollywood Bowl with the Los Angeles Philharmonic in an all-Gershwin program.
For many young people, meanwhile, Feinstein is a bridge to a world the rock era has largely overlooked: a gentler age of memorable melodies and gemlike lyrics.
``Younger people are turning more and more to this other kind of music, because they're getting the things they need from it,'' Feinstein told me as we sat in the fabled Algonquin lobby, near that hotel's Oak Room where he was performing twice a night.
``Gershwin and Rodgers and Kern and Vernon Duke, Harold Arlen -- they all wrote music that affects people in the heart, in addition to having 40 years of memories connected with them. It's therapeutic. Their songs are written to create the effect of joy and enthusiasm . . . .
``I think contemporary music reflects what's going on in the world, and that's why we now have chaotic music -- music with values on the beat instead of the lyric -- or dissonant music, or punk, or whatever. But many young people are realizing that there is a different type of music that helps them express another part of their personality.
``Music affects people more than they realize. I always perform with the intention of reaching the hearts of people, of creating some sort of harmony in their lives.''
Feinstein's theories come delightfully to life in his performances. At a recent session in the mellow ambiance of the Oak Room he had a sophisticated audience both amused and entranced as he played the piano and sang into the mike, wearing a smile that seemed to say this is what life is all about. His clear, refreshingly unaffected voice delivered songs like Gershwin's ``Someone to Watch Over Me,'' ``Our Love Is Here to Stay,'' and `` 'S Wonderful'' with a boyish elegance that worked equally well with love themes and comedy numbers.
He grinned fondly at some of the gymnastic lyrics (``S' exceptionelle,'' ``s' no bagatelle'') like an amused parent at a child doing somersaults, but the heart of the numbers remained glowingly intact in his reverent hands. And Feinstein linked the songs in a chain of comments (``I know what you're thinking -- they don't write them like that anymore''), anecdotes (including snippets of his own life story), and modest jokes that place the music in its show-business setting. After finishing Gershwin's ``Embraceable You,'' he introduced Ginger Rogers, who first sang the song in the 1930 Broadway musical ``Girl Crazy.''
Feinstein's winning style springs from a single-minded commitment to show tunes that has been a theme throughout his life and career. His virtually encyclopedic knowledge of the field was extensive enough to earn him the friendship and admiration of the late Ira Gershwin, George's brother and lyricist. For six years they worked together cataloging the Gershwin oeuvre.
At one point, Feinstein recalls, ``I was cataloging his phonograph records, and I was humming the verse of an obscure song called `Beginner's Luck.' Ira's back was to me, and he was reading the paper, and he kind of froze. He wheeled around in his swivel chair and said, `Mike, that's the verse of ``Beginner's Luck''! I wrote that with George. How do you know it?'
``I said, `Well, I know a lot of your songs.' Then he started quizzing me, and he became amazed. He started telling me stories and giving me pieces of sheet music. He would play me a record and say, `What's wrong with this interpretation?' It was a lot of fun.''
Feinstein remembers vividly the time he was first bitten by the Gershwin bug. It was while he was growing up in Columbus, Ohio.
``My parents had purchased this Andr'e Kostelanetz album, and one of the bands was the main theme from [Gershwin's] `Rhapsody in Blue.' I had never heard music that did what that music did to my insides, and I thought, `What is this? I want to find out more about it.' From there I started listening to as much Gershwin music as I could find.''
The first steps toward a career came when Feinstein left high school. ``It was an important time, because I didn't know what in the world I was going to do with my life. . . . I worked at Ohio State University playing improvisational music for dance classes.''
Confused and directionless, Feinstein moved to Los Angeles when he was 20. ``I had never been there,'' he says. ``I don't know why, to this day, I decided to move there, except I feel there was something that told me I should, some sort of guidance. I believe very strongly that we are all guided by a divine power that is always giving us information if we can pick up on it, that sometimes filters through to our consciousness. But I find that sometimes we have to work toward getting the information that's given to us.''
After making the fateful Ira Gershwin connection, Feinstein says, ``I performed from time to time, and eventually started playing at Beverly Hills parties, where I discovered I had something important. . . . I would know an obscure Gershwin song, and people kept saying, `How do you know these songs?' It made me aware that what I always thought was a weakness -- in concentrating on this older material -- was actually a strength.''
But after Ira's passing in 1983, Feinstein's life hit another low point. Because of a legal dispute, he had to stop his work on the Gershwin material.
Then in February of 1983, he started performing again -- especially at parties, ``and people like Liza Minnelli started to come in to see me,'' he remembers. Minnelli threw a party so Feinstein could become better known. Several celebrities saw his obvious gifts and took him under their wings. From then on his reputation began to grow.
At some point, Feinstein says, he'd like to sing the works of a different composer entirely -- himself. ``I'm writing music,'' he says, ``and eventually I hope to perform my own work. Primarily music -- I'm less adept lyrically. I'm working at it, though.''