There are some groups who feature upright bass, like the Chris Norman Ensemble, Lunasa, or the Breton group Koun. But in all these cases, there’s also a guitar present.
Wouldn’t bass alone make for good accompaniment? It has great drone possibilities (especially bowed) and the ability to create modal and harmonically vague underpinnings for the tune. It has good rhythmic capabilities, too. On the other hand, the sound might get swallowed in a session…
Any thoughts on the use of bass in Irish music? Other stringed instruments (guitar,'zouk…) have become quite common and generally accepted…Why not the bass?
Part of it is ergonomics - the darned things are awkward at sessions.
I think part of it is also the stigma of bluegrass and oldtimey music - there’s the sense that bass is there for that boom-chuck I-V pattern that many feel is inappropiate for Irish music.
Need I say more than : Paul O’Driscoll ?
I really think Worm has it with the fact that is is so damn big. I think it has gone out of style like the Piano, the two are not easily portable therefor akward at a session and more likely to be heard in recordings.
Some hungarian traditional bands have what I think is an incredible bass sound, which actually comes from a cello with a flatter bridge and (maybe) only three strings.
It’s played with a short bow, with four-on-the-floor chords or triads: Whump whump whump whump. Gives an incredible drive to the music. I’ve always thought that would sound great in a ceili band, if you could figure out how it’s done.
Celloes for Irish trad absolutely rock if the player is good - a guy I know locally plays oldtime (I think), and he went up to Swannanoa this summer - He treated it more along the lines of a bass bouzouki than anything else. Lots and lots of tasteful but interesting chordal backup. He strummed it. I wish he would start going to sessions.
ON the piano issue, in these parts we regularly have one or two “casiowhackers” and it works quite well. Again, it depends on the player more then the instrument.
http://www.digitalpressure.com/catalog/album_detail.cfm?album_ID=228
As an admitted PK (Portable Keyboardist, not Preacher’s Kid), in group situations, I usually put my Yamaha on one of the portable organ settings and noodle away at the bass line with my left hand, a la Ray Manzarek (that way you can simultaneously play and drink your Guinness or your double-shot latte, depending on where you are having your session 
). I often wonder how that would sound in an ITM session. Anyway, it should contribute something to the music without overpowering or interfering with any other players.
They’re big, they’re cumbersome, but they do indeed contribute! Or at least that’s what most people tell me when I don’t play mine (it’s awaiting cosmetic surgery that is awaiting spring, when the fumes and dust won’t send me into spasms of misery).
As with most instruments, played appropriately, it can contribute a very good flavor and is a bood base 
for the rythym.
Of course, since min’es been ‘in the shop’, I’ve been able to concentrate much more on the whistle. I do miss her though.