A dance

Late one autumn afternoon I happened upon four young long-haired musicians standing on a windy corner in downtown San Francisco and playing an old country music favorite of mine, ''You Are My Sunshine,'' to a large crowd of people.

Two fellows were twanging away on guitars. Another was plucking a huge bass fiddle. And a girl was sweetly scraping an old square-dance fiddle.

They were all dressed alike. Scuffed cowboy boots, faded jeans and jackets, and wide-brimmed, roomy cowboy hats like the kind worn by one of my old-time movie heroes, the cowboy who made ''You Are My Sunshine'' famous, smiling Gene Autry.

It was wonderfully corny just to stand there tapping my city toes to the beat of the music.

And it was amazing to see people of so many different ages listening. There were very small children with homemade necklaces of pretty leaves looped about their necks. Young people decorated with beards or beads or headbands they'd earned for making it through the perils of adolescence into their twenties. Not-so-young people buttoned into their careers or booked up with social engagements. And even old people standing on tiptoes or cocking wrinkled ears. There seemed to be a little something for everybody in the old mixed bag of country music.

When the musicians finished playing the song, everybody applauded wildly. Then the fiddler asked the crowd, ''Who's got a request?''

By the most delightful chance, I and the person next to me, a warmly bundled, tiny old lady, called out at the same time, ''Tumbling Tumbleweeds!''

''Right on!'' said some others in the crowd, applauding this swift and united action. The musicians struck up the song.

Giving me a friendly pat on the arm, the lady smiled up at me and said, ''I love this song. It takes me back to the days when I was a girl in Wyoming. It was played at all the dances, you know. I went to every one. If there weren't enough boys, we girls danced with each other.''

Her face was round and worn, full of the sweet modesty of plain old age, but I had the feeling that in her youth she had been very beautiful. I saw the look in her eyes, a play of almost girlish sentiment and wry wistfulness, and I knew she was remembering a lifetime.

I'm a shy person but sometimes I do things that are unusually bold; I surprise myself. Returning her smile, I said, ''Since we're partners in requesting, maybe we could be partners in dancing, too? Would you do me the honor?''

''You know,'' she said, beaming at me in a grandmotherly way, ''I just might. It's been ages since I danced to that song.''

Gladdened, I asked the people around us please to move back and give us a little dancing room. It was only the two-step I could do, nothing fancy, but that was all right with the lady. Taking her hand, I held her waist, and together we danced. In the movies you wouldn't see such a dance, slow, fragile, at times awkward, but it had the blessing of the past and the kindness of music.

When the song was over, not only the crowd but the musicians, too, applauded and even cheered.

''I think,'' said my partner, winded and Wyoming-eyed, ''we were a hit!''