I think that we have many roles.
If in an ensemble like the one in which I play right now, the major role is to provide a nice, solid foundation, adding fullness and depth to the overall sound, setting the stage for chordal movement, the foundation and core of the phrase for the ensemble and to pick up and change that variable sound to imitate all of the other bass instrument parts, and appropriately color sound when the players are gone or can't play them. Also, because the sound of the tuba (and the tuba itself is such a variable shaped and sounding instrument) the tuba has an amazing ability to set a mood. Somber, bright, humorous there is a broad palate with which we work. It is so interesting that we have successful tubists and tubas of all shapes and sizes even within the same key. Just look at (and hear) the difference between a CC Mirafone 184 and the CC Chicago Yorks.
If you are a soloist or have frequently exposed parts (no pun intended..

) one can add to that being producing a beautiful tone and phrase which makes people forget they are listening to a tuba. I heard/spoke with Pat Sheridan on Saturday and Sunday...It is strange to think about, but for him the tuba is primarily (almost exclusively) a solo instrument. That must really change the way one thinks about the role of the instrument and playing music.
Besides being faster he is an amazing musician with phrasing that reminds me of a great operatic singer. Actually, I listened to a bit of the MET opera broadcast on NPR after hearing him and I thought that it was some semi-local college kids screeching away. He was way better live than on his CDs.
So, when I'm playing in an ensemble, I'm thinking differently than when playing a solo. When I'm playing a solo, I'm trying to achieve beautiful phrases and to get around all of the technical problems so that nobody can hear that it could possibly be challenging to play the music I'm playing on the tuba and/or think that the tuba isn't every bit of the " solo instrument " (and more) as the trumpet, or the horn. I'm still working on this and I probably will never achieve it, but I'll be working on it.
