When Eddie and Mazie Feinstein moved to a new house in Columbus, Ohio, more than 20 years ago, they had a dilemma: should they take their limited funds and buy furniture or should they blow the whole wad on a piano. Mazie, a former tap dancer with a practical streak, argued for a sofa and chairs; Eddie, a one-time singer with local big bands, now a meat salesman, said, "Let's get a piano. Maybe Michael would play."

Michael Feinstein would play all right -- he's self-taught -- and Michael would sing. The prote'ge' of the late Ira Gershwin is doing both at the Algonquin Hotel, impressing critics and composers (Cy Coleman, Betty Comden, Charles Strouse and Leonard Bernstein, who said "It's in his bones, it's in his bones"), celebrities (Sylvia Syms and Margaret Whiting) and civilians. But it isn't just Feinstein's playing and singing that audiences are applauding; it's his encyclopedic knowledge of songs from the 1920s and '30s -- show music in general.

Indeed, the 29-year-old, who until two weeks ago says he'd never heard a Springsteen song, has nothing to do with the music of his generation -- no rock songs, no schlock songs, he assures listeners in his opening number. It's Rodgers and Hart, Kern, Sondheim, and Gershwin -- especially Gershwin -- all the way.

"The first thing I heard by Gershwin was 'Rhapsody in Blue' on an Andre' Kostelanetz record -- my parents were very middle America -- when I was 9 or 10," says Feinstein, sitting in his publicist's Upper East Side apartment. "When I heard that, something happened in my stomach that had never happened to me before."

Not that "Rhapsody in Blue" was Feinstein's first exposure to the music of the period. "My father had the kind of music memory where he remembers every song he's heard from the time he was a kid," says Feinstein. "He was born in the '20s and remembers songs that were hits in the late '20s and '30s so I learned from him.

"And when I was 5 my parents took me to Goodwill Industries because they had stacks of old records and you could buy 20 of them for a dollar, and I would pick out the records by the pretty pictures on the labels. So I started listening to that music when I was quite young and -- it sounds hokey now -- but I used to watch Lawrence Welk."

A childhood spent watching Lawrence Welk, attending barbershop quartet gatherings with his father to revel in the harmonies, and listening to Beatrice Kay sing "Hello, My Baby" is, almost by definition, an alienated one. "I was very much alone," says Feinstein. "I didn't have too many other friends and those records were my friends. It sounds very sad, doesn't it?

"I went through an agonizing period, particularly in high school when I felt I should be listening more to the radio and enjoying contemporary music. I was listening to Al Jolson and Bing Crosby. My friends couldn't relate to me. I was considered really odd." Even being the youngest drama club president in the history of the school didn't help much.

Two things gradually became clear to Feinstein: college wasn't in his future and Columbus was going to be in his past:

"I knew I had to get out. I felt like I was drowning. I didn't think I could do anything with my musical abilities because I was so isolated from everybody else in Ohio." Feinstein moved to Los Angeles almost 10 years ago. "I still don't know why I chose L.A. I knew Ira Gershwin lived there."

Feinstein didn't really expect to meet the man once referred to by a BBC radio announcer as "George Gershwin's lovely wife."

"I didn't think it could possibly happen. I had heard he was so old and so ill that he would most certainly be dead by the time I got anywhere near."

Feinstein worked in a record store and spent his spare time picking through the bins in old record stores. In one, he found a stack of acetates that had belonged to Oscar Levant and bought them for $150. Then he called Levant's widow June, who hired the 20-year-old to help catalogue the Levant memorabilia. She also paved the way for Feinstein's introduction to Ira Gershwin.

"It was the most exciting moment of my life," he says. "June told me to call Ira's wife Leonore because they wanted to meet me. She asked if I knew where the house was and I said, 'I think so.' She gave me the address but of course I knew exactly where it was because I had driven by so many times. I wasn't going to let on, though.

"I was shaking as I pulled up to the house. When Leonore opened the door, I saw Ira sitting at the table and my heart almost stopped. Ira was reading Variety to see which of his friends had died that day. It was a ritual.

"I was trying to make conversation with him. On the back of Variety was a picture of Peter Frampton and Ira asked if I knew who he was and I said 'Well, I've heard of him' and Ira said 'Is he any good?' and I said 'He's okay. He's not as good as Gershwin.' "

That afternoon, Leonore showed him a closetful of records that Ira wanted organized, catalogued and cross-indexed, a task Feinstein rashly agreed to take on for $500. A year later he was still working on the project, but by that time he was on a weekly salary. Indeed, it was a year before Ira Gershwin learned that his young discographer was a walking encyclopedia of musical arcana.

"The real turning point of Ira's awareness of my knowledge of the Gershwins was when I was sitting humming the verses of 'Beginner's Luck,' " said Feinstein. "He was reading his paper and I started to hum the song and he said, 'That's "Beginner's Luck." That's the verse to "Beginner's Luck." I wrote that with George in 1935' and I said 'I know' and he said 'How do you know?' and I said 'I know' and he said 'How do you know?' and I said 'I know a lot of your songs.' Then he started quizzing me to see how much I did know, and he was really surprised."

With the aid of his nurse, Gershwin began coming downstairs earlier and earlier each day to wait for Feinstein's arrival. "He would tell me stories and find things of his to autograph to me. He would cut out George's signature from canceled checks and put it on sheet music for me," said Feinstein, who returned the favor by performing for Ira on the piano George used to compose "Porgy and Bess."

"Everybody in the world Vladimir Horowitz, Harold Arlen, Burton Lane played that piano so I felt I got energy from the keys," he says. "I would find Ira's most obscure songs and play them for him because he got such a kick out of it.

"It became a very intimate relationship. It was paternal. Ira had never had children and he had always wanted to have them. He would have been a wonderful father. He'd always say 'How are you today, m'boy?' He was so loving and caring."

Feinstein found his career as discographer and archivist expanding to include "evening's entertainment," when friends of the Gershwins' began hiring him to play at Beverly Hills parties. When his specialty became more widely known, others sought him out. He introduced conductor Michael Tilson Thomas to Gershwin, and it was Feinstein who wrote the liner notes to Thomas current recording of "Rhapsody in Blue."

Ira Gershwin died at age 86, on Aug. 17, 1983. Feinstein was with him one day earlier.

At one Beverly Hills soiree, Feinstein met Liza Minnelli, who took him under her wing and "presented" him at a gala at Le Mondrian Hotel in Los Angeles, had him as her accompanist on a "Tonight Show" appearance and acted as hostess for his recent Algonquin opening. At another party, Feinstein met publishing magnate Walter Annenberg, who hired him to play at his 1985 New Year's Day party honoring the Reagans.

"I was trying to think of something special I might play for the president, and I knew the theme music from his movie 'King's Row.' He recognized it and said, 'That's the best movie I ever made. Nancy, I have to tell Nancy.' It made a big impression.

"Then, after dinner they had a sing-along with Charlie Wick conducting," recalls Feinstein, adding that the head of the United States Information Agency, a former William Morris agent, has perfect pitch.

Wick was at the Annenbergs' Palm Springs home again this past New Year's Day and Michael Feinstein was back, too, for a return engagement.

"Mrs. Annenberg was concerned that people wouldn't sing along again," he says. "But right after dinner Mr. Reagan couldn't wait to get to the piano. I was playing 'Carolina in the Morning' and he was singing 'Nothing could be finer . . .' He just couldn't wait, and it was so much fun for me to see. He stayed by the piano the whole time wanting to sing song after song."

How would Feinstein rate Reagan's voice? "Well, he doesn't make a living as a singer, but he can carry a tune."

Feinstein's fans include Nancy Reagan, according to her press secretary, Elaine Crispen.

Others gush with enthusiasm. "He plays like a virtuoso and sings like an old-timer," says Irving Caesar, lyricist of such songs as "Tea for Two." "I feel like he's my son. He doesn't know it but I've adopted him."

"He's an extraordinary pianist and singer and above all an archivist of wide knowledge," says Betty Comden, who with her partner Adolph Green wrote the lyrics to such shows as "On the Town" and "Bells Are Ringing."

Reviewers compare Feinstein to a young Bobby Short, or Steve Ross -- comparisons that delight him. "The first person I heard do this sort of music was Steve Ross," he says. "I'd never heard anyone do that, and I thought he was just magnificent. He was a very great influence because he had such excitement for what he did. Bobby Short is the originator of this style and I couldn't exist without him. He has single-handedly preserved most of this music in an authentic fashion."

After his open-ended engagement at the Algonquin, Feinstein plans to record a series of duets "with my favorite lady singers: Margaret Whiting, Gogi Grant and Liza." He hopes to be performing in Los Angeles and elsewhere.

In the meantime, he's writing some songs of his own -- "but I'm not ready to perform them yet because I have very high standards" -- and trying to learn more music. "This field is a bottomless pit and even with the familiar songs you can find extra lyrics. It's never ending." He's also busy trying to convince people that no, he doesn't claim to know every song. "People will come up to me and say, 'My aunt Bertha used to sing this and I'll bet you don't know it.' " A pause. "I do know a good number of them though."

Feinstein is confident that people of his age will come to know -- and love -- these songs, too.

"Linda Ronstadt has a lot to do with it," he says, referring to "What's New" and "Lush Life," her two hit albums of standards. "I'm not mad about the way she sang those songs. I think they're heartless, but there'll be enough people who will discover them for the first time through her and later discover the sublime interpretations. There are just basic eternal values in this older music that people will turn to more and more. I don't disparage contemporary music. It just doesn't feed my soul the way this other music can."

Whether his are sublime interpretations, Feinstein leaves for others to decide. "I do try to be as faithful to the songs as I can in terms of trying to put across the writer's original intentions. I know the things Ira liked pointed up in a song.

"I'm sorry he's not here in the flesh, but I believe he's around," says Feinstein, whose unofficial signature song is "S'Wonderful."

"I feel his presence."