Thaddeus Cahill (June 18, 1867 – April 12, 1934) was a prominent american inventor of the early 20th century.

He is widely credited with the invention of the first electromechanical musical instrument, which he dubbed the telharmonium.

That year he established a laboratory at Holyoke, where he was joined by his brother, Arthur T. Cahill, and where the two would first demonstrate the teleharmonium to a public audience.

[1][2] Cahill had tremendous ambitions for his invention; he wanted telharmonium music to be broadcast into hotels, restaurants, theaters, and even houses via the telephone line.

$5,514,000 today), only three telharmoniums were ever built, and Cahill's vision was never fully implemented.