I do, from time to time, introduce a song with "program notes," if I feel that it enhances the audience's enjoyment of the song. But never more than the brief comments you might find on the back of a record jacket.

It's a major boo-boo to fall into the category where it can be said of you that, "I knew he was a folk singer because he spent fifteen minutes introducing a three minute song."

I've heard people do that sort of thing. Bad!

Don Firth

P. S. I heard once heard one guy rattle on for about ten or fifteen minutes and then forget what song he was introducing!!   Not cute! But it was pretty funny. Not the way the singer would have intended it, though….