How many jazz musicians does it take to change a lightbulb? None. Jazz musicians can't afford lightbulbs. "Don't worry about the changes. We'll fake it."
More seriously sometimes whatever the individual artist playing completely solo does it's just not enough especially if they are not lit up inside let alone thinking about flicking a switch. You might get the intimate, extraordinary vision of a single person on the stage playing whatever instrument or singing and that is completely enough. Solo piano for instance works in a jazz or improvised music context supremely well.
And yet you want to witness the interaction. You want a big crowd of players perhaps or just a decently-sized group instead. And isn't ''people improvisation'' and the alchemy of personality feeding into this another thing again on top of what one person can offer? A further question spools out from this: is there at all an ideal size for a group of jazz musicians to come up with the ideal results?
I'm not certain that there is. However, different combinations certainly work in particular situations better than others. It's hard to beat a jazz-rock group when there are at least five or six people on stage involving electric guitar, heavy bass and a sax or trumpet leader. A huge herd of saxophonists might even achieve results you didn't think were even possible. Or what about just the one, all alone poking the bell of their saxophone into a microphone?
Classic hard bop really needs at least 2 or even better 3 horns in the front line plus a rhythm section in tow. As for big bands it doesn't matter if it's a standard big band set-up or not. In some ways a smaller octet or nonet is quite enough. If anything by contrast small-group jazz is far more satisfying. A duo, say trumpet and guitar can work just as well as two guitars. A singer and a trio is a classic format or a piano trio on their own is just as good and one of the most ideal formats. A solo sax concert by Evan Parker might change your life. Ponder on that.
But what matters in a group is when there is true interaction within this body of players. A soloist using the other musicians as accompanists or a support eco-system isn't all that interesting beyond enjoying the sheer skill and ideas of the leader. What is interesting is sometimes going to a gig drawn to it by the leader's name but emerging much more taken by say the drummer or the bassist whose names you were only at best dimly aware of beforehand and yet as you discover inspired the whole thing and provided that crucial spark for its success.
Musicians will not readily admit it, especially improvisers, but things become stale when artists just start playing long-since memorised patterns and quick hacks so that they can produce the effects they need without really pushing themselves hard. As an audience member you can usually tell when musicians are stuck for material. Improvisation is often misunderstood as a concept and when bands are playing complex composed pieces the space for improvisation is often highly limited although the language and interpretation is still often loose and open enough for exploration beyond the composer's exact intention.
So when what the artist does isn't enough it's not about format or groupings or this or that instrumentation necessarily. It's really and this is why it becomes so difficult to pull off the feat and few can do it a performance has to have some sort of presence that makes it unique to that occasion and the spark of originality has to be there so something will then follow. It's what free improvisers really crave. They don't want a secondhand experience. They want to embrace risk and understand that not everything will work and the process is important as much as the outcome. But basically they are willing to try and it's not a random laissez faire thing at all. And this desire is not even applicable solely to free improv. Again if there is genuine interaction and some sort of chemistry and understanding on a deep level between bandmates this is the kind of factor that adds to a performance and just can't really be translated to a record so easily especially nowadays when so many artists go into a studio independently to do tracking or even play together online remotely and everything is then pieced together. Think about what your ideal size is. And would that last gig you attended have been even better if there were more or even fewer musicians on stage instead?