The Only 'Folk Music' Movie Musical?

In the 50's and 60's there were a number of rock n'roll films like this, as well as several country music and rhythm-and-blues ones, thin storylines with mainly just an excuse for popular (and usually quite a few obscure) singers of the genre to simply perform songs on the screen. HOOTENANNY HOOT however seems to be the only movie of this type that features folk music. Does anyone know of others? It's kind of a surprise only one was made given the folk scene was quite big for a few years in the mid 1960's, indeed major studio MGM made this film whereas the other genre musicals often came from independent companies.