They could even have two kinds, [Gnomish Stereophonic Audio Replicator] and [Goblin Blaster].
I'd think it would be an engineering item. Sits in your inventory, and when you select it and a spot on the ground, it would temp-spawn the appropriate boombox there, which would then disappear after x minutes or when canceled, and it can of course only spawn one at a time. Somewhere between the game's fishing mechanics and its dynamite mechanics I guess?