One other thought about communal composition. There is one instance that I can think of that sort of vaguely resembles that idea. That's the work of the Almanac Singers.

One observation is that most of what the Almanacs wrote was less than memorable. There is, to my mind, one exception. That one exception is "The Sinking of the Reuben James." As far as I know, it has never been collected in the field, but Ed Cray was of the opinion that it might become tradtional (based on the tune rather than the now-dated text).

But what is the history of Reuben James? It started with one writer (Woody, of course). He had a long text, no chorus, and the tune of "Wildwood Flower" (one of Woody's many borrowings from the Carter Family).

When he brought it to the other Almanacs, they were not impressed. It was too long (it listed the names of all the dead), and it didn't have a chorus for everyone to join. They told Woody that it had to change. They got him to chop down the lyric.

And the chorus? That's disputed. Some say Woody produced it, using a variant on the "Wildwood Flower" melody. Some say it was Pete Seeger's. Seeger at least once said it was Woody's. My personal guess, combining the statements and based on the skill sets involved, is that Woody wrote the words and kept the "Wildwood Flower" tune, and Seeger modified it to what we have today. But that's only a guess. In any case, Woody was involved.

Communal composition? Yes, in the sense that many hands were involved. But the basic tune was borrowed, and although the text was much argued about by the Almanacs, all (or nearly all) of the actual words are Woody's. The idea was Woody's. In a very real sense, Reuben James as we had it is just Woody's text put through a very high-speed folk process. The community was involved. But Woody mostly wrote it.

Then Fred Hellerman added a verse. Again, standard folk evolution.

I'd call the result a modified Woody song, not a communal composition. And yet, it's about as communal as a song gets!

Incidentally, one can see the process continuing even after the song was nominally finalized. The Almanacs were not an instrumentally strong group. (Yes, Pete Seeger had almost a savant skill with instruments, and one or two of the others were all right also, but a bunch of them were singers only.) The result is a recording which is mostly driven by the vocals. That's somewhat true of the Weavers recording, too. But... well, no one cares how I sing it :-), but I'm only one voice and I'm probably a better picker than anyone in the Almanacs except Seeger. So the way I sing Reuben James is a lot more driven by my 12-string guitar than my voice -- I give it almost enough "drive" to be a bluegrass song. I don't say it's better or worse; it's just that songs change form depending on context. And that is folk process, too!