The acts are The "New" Main Street Singers (a group of nine similar to the New Christie Minstrels, only one orginal member left, still around and playing second-sting amusement parks), the Folksmen (a male trio, retired from performing, and Mitch and Micky (a "cute couple," driven apart by Mitch's descent into paranoid depression). (Although we could think of lots of analogs for the Main Street Singers and the Folksmen, Georgie and I had a hard time thinking of any male-female duets from the era that resembled Mitch and Mickey--our closest guess was the Carpenters, although they were more of a pop act, with Mitch barely surviving a mental illness, unlike Karen Carpenter.) In these films, the dialog is entirely improvised, which makes some of it wonderfully goofy, while some other of it is lame. The Folksmen's reminiscence about their second-rate recording label that issued records without holes is one of the funniest bits although totally improbable. On the other hand, Bob Balaban, who plays the reunion organizer, drives his "noodge" character so far into the ground that it's a positive relief when one of the other characters swats him. Fred Willard as Mike LaFontaine, the Main Street Singers' manager, overplays the part of an obnoxious asshole to the point he's painful to listen to, and one brief appearance of the character would have been sufficient.
On the other hand, Eugene Levy, who plays Mitch Cohen, does a frighteningly good job of portraying someone who's had a few too many doses of Thorazine. The uniformity and believability of his character throughout is truly remarkable given the improvised nature of the script.
The musical score is also worth comment, since the performers wrote and performed their own music, which reproduces second-rate 1960's folk music very well--not good enough to be really good, not bathetic enough to be really dreadful, and not obviously parodying other songs (though I do think that "Never Did No Wanderin" has great potential to be filked).
All in all, the movie was generally sweet, funny, and appreciative of, if not reverent of, its source material, which is the kind of satire I like best. Recommended if you liked folk music at all.