The ammo and gun looks like maybe the “Dushka” which is the Russian counterpart to the .50 cal @ 12.7-mm: en.wikipedia.org

IIRC, the “Chicago piano” was the quad array of 1.1” guns used for AA on U.S. ships until superceded by the quad 20-mm oerlikon and 40-mm Bofors (neutrality is profitable): navweaps.com

“Chicago typewriter” referred to the chatter of the Thompson .45, but the musical portmanteau may have evolved from the movie cliche of gangsters concealing their Tommy guns in violin, or more likely, the larger viola cases. I supposed you’d need a double-bass viol case to tote an M2 around in.

I guess that thing ended up in the stairwell as the goons were trying to get it to the roof.

Allahu Ack-Ack!