The imagination is often figured as a site of infinite possibility, free to create without regard to material limitations. But touring the museum of imaginary musical instruments suggests that there are in fact certain grooves that form over time to channel the course of fantasy. Futuristic imaginary instruments flow along one such groove. The future orientation of the imagination directs its energies to the technologies synonymous with “progress” in the present – an effect that starts to show its peculiar limitations when one looks back at projections like the hot air balloon of 2440. This particular channel for technological fantasy was not always so deep. Before the eighteenth century, imaginary instruments typically appeared either in a contemporaneous foreign land (like Bacon’s sound-houses) or in the past, as devices that existed but had been lost (like the tubo cochleato). The museum of imaginary musical instruments thus illuminates not only the intersection of reality and fantasy, but also the unknown history of the imagination. It reveals numerous paths of inventive thought not taken — paths covered up by years of “progress”, but which, when cleared off, might yet lead us back to something new.