Greetings!  Several years back, I ran into a vehicle such as you
describe.  It was in a collection at "Old Bills" in Liberty, Missouri.

It was a 1912 Case truck which had been constructed for parade use.
The back was like a Model T Ford Depot Hack, or vegetable truck, and
it would seat six people.  I don't know if the calliope was a Tangley,
but there was 24 pipes, 12 on each side, mounted just even with the
windshield, and the base mounted with the bottom of the windshield.
The keyboard was mounted inside on the passenger side.  I'm not sure
how the pipes were blown, as they wouldn't let me raise the hood or
crawl under it.

The whole outfit was in really good shape, and there was still visible
the advertising of a music company that it was built for.  It was not
for sale at the time I saw it, but the last I heard, someone back East
bought it, and I lost track of it.

Does anybody out there know where it is?  The truck itself is very
rare, since Case built very few of them.

Paul E. Freiling
Fullerton CA