Cahill's invention used massive rotating dynamos to generate electrical signals that produced musical tones, transmitted live through telephone wires to hotels, restaurants, and private subscribers. Though commercially impractical and eventually abandoned, it anticipated synthesizers, Muzak, and the entire concept of music delivered as an electrical signal decades before radio broadcasting existed.
Housed in a building on Manhattan's West 56th Street, the Telharmonium weighed roughly 200 tons and required its own power plant to run. Cahill envisioned it replacing live orchestras in public spaces, streaming 'electrical music' through the existing telephone network directly into homes and businesses, a strikingly prescient idea decades before anyone imagined broadcast radio, let alone streaming audio.
The device worked by using alternators to generate alternating currents at specific audio frequencies, which were then combined and shaped to approximate the timbres of orchestral instruments. Diners at the Café Martin and other venues heard eerie, organ-like music apparently emanating from telephone receivers mounted around the room, a sensation at the time.
Ultimately the Telharmonium's phone-line transmissions caused crosstalk interference on the telephone network, angering other subscribers, and the sheer expense of building and maintaining it bankrupted Cahill's company within a few years. Yet musicologists and engineers now regard it as the first electronic musical instrument of real ambition, a direct conceptual ancestor of the Hammond organ, the Moog synthesizer, and every streaming music service that followed.