It was as common as buying a newspaper. At night the trolley would let you off near the corner newsstand, which also sold sheet music -- all the latest tunes. Department stores and dime stores had sheet music, too. You couldn't get into Woodies' in those days without stumbling over the piano player in the lobby. A customer could take some music off the rack, hand it to the "demonstrator" -- don't knock it, that's how George Gershwin got his start -- and ask him to play. If the song struck the customer's fancy, he'd take the music home for his wife or sweetheart.

That's how they courted then: In those pre-premarital, pre-martini days, when a fellow came to call, his "intended" would entertain him (and, incidentally, show off her cultured upbringing) by playing the piano. At parties they's roll back the rug and dance while someone played.

Someone always knew how to play.

Sheet music, and the way of life it represents, has gone the way of the lace doily. Which is all the more reason to collect the stuff, says Daniel Priest, an area collector who just won't let the music stop.

"It was a simpler time," says Priest, a public-relations consultant from Chevy Chase who found sheet music while chauffeuring his antique-dealer wife around the countryside. "A lot of the songs are very sentimental. There are lots of tunes about granny's gray hair, mother at home and the cat on the hearth -- no, that's not a song title, but it could be. They're all very sweet thoughts."

He flicks through one of the teetering piles of old sheet music stacked on tables, under benches and on the floor of his wife's Kensington antique shop. "Look at these -- 'The Baby's Prayer at Twilight,' 'The Little Grey Mother Who Waits All Alone.'"

But it's more than campy nostalgia that spurs collectors on. "You get a history of the country that's documented almost beyond belief," says Max Wilk, a Connecticut writer and collector whose book on sheet music, "Memory Lane," was published in 1977. "You get all the political attitudes and changing social mores. You get World War I, the invention of the airplane, the automobile, the telegraph. You get women's lib in 1915. There are Italian songs, Jewish songs, Irish songs and what they used to call 'coon songs.' You get everything in American history over the last 80 years."

Part of the thrill is in the hunt. Wilk stalks flea markets for his special interest, Irving Berlin songs. "Some day," he says, "somebody will find the sheet music for Irving Berlin's first song, which he wrote in 1906. There were maybe about a hundred printed, and if anybody can find a copy of 'Marie from Sunny Italy,' he's got himself an American treasure."

They still make sheet music, Wilk says, but it's just not the same. "There's no excitement in it anymore," he laments. "It's a terribly dull business today. Now they do mostly folios -- put out a book of somebody's greatest hits and sell it for five or six bucks. The whole sheet-music business has kind of gone away."

Ah, but when things were hot. . . During its heyday, about 1890 to World War I, millions of pieces of sheet music were sold, and according to Priest most of it is still sitting in people's piano benches. "People hang onto that stuff," he says. "They don't know what it's worth."

He and his wife, Lorna, do. They've collected about 5,000 copies of sheet music, most of which they sell for $2 or $3 apiece.

It's categorized by subject: women's first names, old movies, states (there's a song for nearly every state), old vaudeville stars, flowers, Broadway shows. You want moons? Have they got moons! "Moonbeams on the Lake," "Drifting Moon," "When the Harvest Moon Is Shining on the River."

Did anybody really ever gather 'round the piano and sing "Kicky Koo, Kicky Koo, You for Me, Me for You"? Apparently so. The Priests' copy is well thumbed.

"The Little House Upon the Hill." "In the Town Where I Was Born."

"I Had to Lose You (To Find What You Meant to Me)." "The songs all had to do with less complicated relationships -- certainly very proper ones," Priest says. "Now it's 'I want ya, baby,' not 'I love you, sweetheart.' Relationships were proper then. 'Love' was not a euphemism for sex."

Oh yeah? What about "When I Wana, You No Wana," with a pouting Indian brave in full headdress that would win a place on any Native American's dartboard. "How we ever gonna make heap love," go the lyrics. "I no can wait a million days / I know another pretty redskin come to my tepee / And she wana make heap love to me. . ."

"They're talking about hugging and kissing," Priest insists. "Look at this one: 'We'll be loving, billing, cooing / Like everybody's doing / When I get you alone tonight.' You can see the values of the time very easily."

In addition to the sweetness and light, there's the hearts-and-flowers angle: sheet music as Art. The covers are Art Deco and Art Nouveau, with a heavy dose of Art Schmaltz. "Some of them are not very awfully good," Priest concedes. "But they're charming. That's the thing about antiques. Look at this. You'd flunk a kid in your beginning art class if he turned in something like this. But it's attractive now, even with its eighth-rate artist, because its Americana."

It's art, it's history, it's sociology. And if all else fails, you can always sit down and play it.