Chicago was home to the reinvention of the harmonica from tiny dime store toy to amplified and distorted Mississippi sax.
One kid drummed on a washboard, another plunked a broom-handle bass, a third faked chords on guitar, another blew into a gob iron (which was what they called a harmonica), and they dubbed themselves a band.
The reason that the harmonica sometimes is called a tin sandwich is that you hold it just like a sandwich.