According to Wikipedia...what!? OK but it comes with my usual beware of Wikipedia warning...

Jules Bass primarily adapted Tolkien's original lyrics for the film's musical interludes, drawn primarily from the songs that feature prominently in the book. He also assisted Maury Laws, Rankin/Bass's composer / conductor-in-residence, in the composition of an original theme song, "The Greatest Adventure (The Ballad of the Hobbit)", sung by Glen Yarbrough as the sole original song written for the film. This folk ballad came to be associated with Yarbrough, who reprised it in the soundtrack to The Return of the King (1980).

Wikipedia

Again I can't confirm the truth of this at the moment, but it feels truthy

Although I liked and was grateful for the animated version , as my little one was able to view it, she may not look at the Jackson one until thirteen, I confess I strongly did not like the melodies of any of the songs. They just seemed so irrelevant to the action. So much like a wandering minstrel I expected to see Robin of Loxley at any moment. And while I am a die hard fan of Robin Hood, he did not belong there!