NEW YORK (AP) _ A tuba can be a thing of beauty, say lovers of the instrument with the oom- pah sound. And 300 tuba players all huffing and puffing away at the same time can draw a crowd, even in cosmopolitan New York.

Thousands of shoppers and sightseers jammed Rockefeller Plaza Sunday to watch what has become an annual holiday concert.

The performers played holiday tunes on tubas of all colors, shapes and sizes. Christmas trees sprouted from the bells of several tubas, while a lighted electric menorah nestled in another.

''Tuba Christmas,'' as this holiday custom has been known since it started in 1974, was conceived and conducted by Harvey Phillips, a 56-year-old professor of music at Indiana University.

Phillips is a tuba missionary and evangelist who has devoted his life to improving the image of the tuba and of tuba players, a minority he believes should not be forgotten at Christmas time.

''People think the tuba is a silly instrument that just goes oom-pah,'' Phillips told The New York Times. ''Tuba Christmas helps us gain public awareness, the first step to respectability.''

There are now 122 Tuba Christmas celebrations around the country organized by Phillips, as well as Tubafest concerts that he has held throughout the world.

''I think there is so much tuba prejudice because it is so big and clumsy and ugly,'' said Rachel Robinson, a 16-year-old in the tuba chorus.

''People throw things in your tuba,'' she said. ''Transporting it is hard. Sometimes we have to put it on the roof of a car or tie it across the hood.''

''Harvey has done more for the tuba than any man alive,'' said Garrett Wright, a 73-year-old double euphonium player, who played in another Tuba Christmas in Akron, Ohio, on Saturday, and then in New York on Sunday.

''There have been amazing breakthroughs,'' he added. ''There is now a man who can do 'Flight of the Bumble Bee' on the tuba. I didn't think I'd see that in my lifetime.''