Lincoln and Music

[RJNorton]

I think we discussed this a while back, but I have forgotten if we came to a conclusion.

"During the Lincoln-Douglas Debates, Lincoln decided to mock the brass band which accompanied Douglas. Lincoln took out harmonica and played upon it. "This is my brass band" he said."

SOURCE: page 151 of Lincoln Talks: A Biography in Anecdote
compiled, collated, and edited by Emanuel Hertz (Halcyon House, New York, 1941).

It this story true or apocryphal?