Tuba or not tuba: That was the question.

After all, it was about 9 degrees at the concert out there on the Ellipse last night, counting wind chill. And as about 12 dozen of the area's most accomplished tuba and euphonium players walked on stage at the "Pageant of Peace" to perform the 10th annual "TubaChristmas" carol concert, one wondered about frostbite -- bite, literally, as they mouthed their big brass instruments.

The players were jammed on a small stage, with the sousaphones in the rear, the letters of "TubaChristmas" emblazoned in red on their huge bells.

Most of the performers elected to play with gloves on -- the tuba requiring less digital finesse than, say, the piccolo. One could also see lots of ChapStick in use during the half-hour show.

The weather was equally hard for the roughly 3,000 intrepid souls in the audience -- some of them sipping cups of coffee and chicken soup to warm their systems -- as they joined in, singing in the repeats of about a dozen carols, including "Joy to the World," "Silent Night" and "God Rest Ye, Merry Gentlemen."

"TubaChristmas" is one of those initially modest, largely unheralded rituals -- started 12 years ago in Bloomington, Ind. -- that just catch on. It is a phenomenon -- one of those free and joyful things like the Kennedy Center's annual New Year's Eve Gala, or even more, New Year's Eve in Times Square, that appeal to the need to observe moments of the season en masse.

This year there are 123 "TubaChristmas" events being held in the country -- from Salt Lake City to Dallas to New Haven -- one of the biggest was at Rockefeller Center last Sunday.

There is also, it might be said, a lot of masse in a gathering of 150 of the biggest instruments in the orchestra; weight alone ranges from about 15 pounds for the euphonium, the highest in range, to the sousaphone, at 25 pounds; and individually, they make as large a sound as almost any other instrument, except, say, for the thunder of the timpani. As one player cracked during a rehearsal break yesterday at a Commerce Department auditorium, "This is a big hunk of metal in this room."

"TubaChristmas" is the brainchild of Harvey Phillips, professor of tuba at Indiana University (the most prestigious of the state university music schools). Phillips noted that the instrument takes a back seat in the symphony orchestra -- literally -- and said that material for it is not sufficiently well known. The euphonium, in fact, hardly makes the orchestra at all.

Part of "TubaChristmas' " immense success must be attributed to the immense gusto of Phillips, a man at an indeterminate point in middle age who has traveled the country promoting this cause -- among other things, as a memorial to his mentor, William J. Bell, who played tuba for Toscanini in the fabled NBC Symphony.

But what is the connection of tubas and Christmas, to Phillips at least? "Well, one is that it suddenly occurred to me that Bell was born on Christmas," he said yesterday.

But another is that these are ideal outdoor instruments. Although tubas are too heavy in tone to play a major role in much symphonic music (though that never stopped Wagner or Bruckner from using them with abandon), they are far better suited to a concert like last night's than is the violin or oboe. So how better to make people take note of the tuba than at Christmas? And it seems to have succeeded beyond Phillips' wildest dreams.

Another such project is the Tubists Universal Brotherhood Association (TUBA for short), with about 2,000 members. The other big event of the tuba year is called "Octubafest."

An additional reason "TubaChristmas" has flourished is the surprisingly large supply of such players in communities almost everywhere, a fact attributable mainly to the tradition of high school and college bands, in which most of last night's players first mastered the instrument.

Members of last night's ensemble ranged in age at the rehearsal from a man who said he was 57 to 10-year-old Abigail Alberstein of the Bronx. She looked barely large enough to carry her euphonium, much less play it. A number of the performers looked like high schoolers.

Additionally, here in Washington there are instrumentalists from first-rate military bands. Brian Bowman, first euphonium of the Air Force Band, shared the conducting with Phillips. And Martie Erickson, first tuba of the Navy Band, was a principal organizer of the event.

Participants paid $5 apiece to register, and could also purchase knit red and white "TubaChristmas" caps or scarves.

One carol was conducted by Channel 9 critic Davy Marlin-Jones, who -- with his usual antic gestures -- looked more as if he were trying to rise in flight above the players than keep them together. But, after all, it was cold out there, Marlin-Jones is inexperienced as a music director -- and remember, even Mstislav Rostropovich came to conducting later in life than most people.

The sound, by the way, of these massed instruments is very beautiful -- massive, rich and smooth.