The harmonium is a type of free-reed organ that generates sound as air flows past a vibrating piece of thin metal in a frame. The piece of metal is called a reed.

More portable than pipe organs, free-reed organs were widely used in smaller churches and in private homes in the 19th century, but their volume and tonal range are limited, and they generally had one or sometimes two manuals, with pedal-boards being rare. The finer instruments have a unique tone, and the cabinets of those intended for churches and affluent homes were often excellent pieces of furniture. Several million free-reed organs and melodeons were made in the USA and Canada between the 1850s and the 1920s. During this time Estey Organ and Mason & Hamlin were popular manufacturers.
Harmoniums have been used in western popular music since at least the 1960’s. John Lennon played a Mannborg harmonium on the Beatles’ hit single ‘We Can Work It Out’ and the band used the instrument on other songs recorded during the sessions for their ‘Rubber Soul’ album. They also used the instrument on the famous “final chord” of ‘A Day in the Life’, and on the song ‘Being for the Benefit of Mr. Kite!’, both released on the 1967 album ‘Sgt. Pepper’s Lonely Hearts Club Band’. Many other artists soon employed the instrument in their music, including Pink Floyd, Nico, Elton John, Tori Amos and Supertramp.

Andrew Powell plays the harmonium on Kate’s song Hammer Horror.