Participated in a couple in the late 60's. Even an accordian player (myself) was welcome. No drugs/no alcohol, just a rolicking good time until the wee hours of the morning. Since we were all amatures we called it a "Nanny-Hoot."

The following is from the Random House Dictionary of American Slang: 1997 p. 150 which notes that the origin is unknown.

2.b. a performance of folk music, esp. by a number of artists with a degree of audience participation. Now coloq. 1957 P. Seeger, in Sing Out (Winter) 34:Another took a tape recorder with her and set up small hootenannies in country stores, and recorded the singing. *1960 Seeger & MacColl Singing Island 1: The kind of songs which are delighting audiences at concerts and hootenannies up and down Great Britain. 1963 P. Tamony, in West. Folklore (July) Under four sponsorships, over seventy-five programs of folk song were presented [in New York City] under the "Hootenanny" title between 1941 and 1960. 1975 Greer Slammer 39: I suppose that means guitars and hootenannies in my chapel. 1988 B.E. Wheeler Outhouse Humor 14: I was singing at a hootenanny.