It's a gathering of tuba players doing Christmas carols. They only had an hour and a half of rehearsal, but they sounded pretty good. They ranged from student to professional, and there were about 30 of them.
The audience was probably between 500 and 1000 people--it looked as though Tuba Christmas had been going on for a least 5 years in Philadelphia (judging from a casual glance at the buttons some performers and a tuba were wearing).
Most of the music was familiar, and I admit I don't remember the pieces I hadn't heard before. The high bits of "Greensleeves" were lovely, and "Fum, Fum, Fum" is especially well suited to tubas. The oompah version of "Dreidel" was fun.
The other effort at inclusiveness was less satisfactory, I think. The director wanted to have a Kwanzaa song, but couldn't find one, so they did "Go Tell It on the Mountain". To my mind, "Go Tell It on the Mountain" could have just been included without comment.
This sort of concert naturally has some lecturing. I know much more about tubas than I used to, and you will not escape. Tubas are available in more sizes and types than I was aware of. Collect them all! There's the little baritone tuba--about 2 1/2' at its maximum dimension. The next size up is the euphonium, and everything larger than that is a tuba, though they come in half a dozen or so different keys and seemed to vary quite a bit in size. Also, the baritone is available in German (oval format) and English (British?)--the perimeter has straight sides and round ends. I don't know whether that shape has a name.
The concert tuba is held in your lap and has the mouth pointing up. The recording tuba was designed for the early days of recording, so it has a (nearly?) horizontal mouth so it can be aimed at a microphone. The sousaphone (the marching band instrument which is my default idea of a tuba) is derived from the over-the-shoulder cavalry(!) tuba.
The tuba was the last instrument added to the standard symphony orchestra, in 1835. I have a weird belief that the lack of change in symphony instruments means something has gone badly wrong with classical music, but I can't explain why I think this lack of new consensuses (consensi?) is a problem, and no one seems to agree with me.
Tubas have a gentle taper in their tubing, like French horns. This gives them a mellow sound rather than the brilliant sound of straight bore instruments like trumpets.
Tuba Christmas was invented about 20 years ago in Indiana (by Harvey Phillips, I think) as part of a movement to get tubas more publicity and respect. The respect side is covered by commissions for tuba music and by brass chamber music groups.
I hadn't realized that Christmas carols are some of the oldest songs (or at least oldest tunes) still in popular use. "O Come, Emmanuel" goes back to the 15th century and is (based on?) Gregorian chant. I feel less cranky about the lack of good new Christmas carols. It's obviously harder to come up with a good one than I thought.
The concert had been featured in Philadelphia Weekly, which mentioned that the participants were encouraged to decorate their tubas, but in fact there was very little decoration--one tuba had a scarf tied around its neck, and a sousaphone had a red ball hanging in the middle of its mouth. This was a bit disappointing, but on the other hand, how much can you decorate a tuba without making it harder to play or affecting the sound?