In his article "Bob Dylan -- a new voice singing new songs" from "Sing Out!" (Oct/Nov 1962), reprinted in "The Dylan Companion", edited by Elizabeth Thomson & David Gutman (London: Papermac, 1991), Gil Turner paraphrases Dylan's statements from the WBAI-FM Broadside show:

While Bob is a noteworthy folk performer with a bright future, I believe his most significant and lasting contribution will be in the songs he writes. Dylan avoids the terms "write" or "compose" in connection with his songs.

"The songs are there. They exist all by themselves, just waiting for someone to write them down. I just put them down on paper. If I didn't do it, somebody else would."

His method of writing places the emphasis on the words, the tune almost always being borrowed or adapted from one he has heard somewhere, usually a traditional one.
ljc