Interesting - potentially silly as the autoharp may be, you are right that it doesn't seem to appear in any of the standard music joke pages. Seems unfair and improper discrimination to me.

Well, here's a bit of a story - at least something to say, if not actually funny. From the "Happy!" file:

Nobody celebrates 9/4/1817 as the birth in Morgenroethe, Germany of Charles Zimmermann. In 1881 he patented, then promoted & mass-manufactured the then-called "Autoharp." He had nothing to with inventing it, however. Seems he stole the idea from a German guy yclept Karl A Gutter who'd patented the thing in England. In the fullness of those gentler, slower-paced days, Zimmermann was run over by a horse-drawn street car & died 10/20/1898.

You may wish to contact Mary Lou Orthey of "Autoharp Quarterly" & Orthey Instruments http://www.fmp.com/orthey. She seems to know as much about the thing as any.