Pump organ

The pump organ or reed organ is a type of organ that uses free reeds to generate sound, with air passing over vibrating thin metal strips mounted in a frame. Types include the pressure-based harmonium, the suction reed organ (which employs a vacuum system), and the Indian harmonium. Historical examples include the Kunstharmonium and the American reed organ, while earlier forms include the physharmonica and the seraphine.

More portable than pipe organs, free-reed organs became widespread in smaller churches and private homes during the 19th century, although their volume and tonal range were limited. They generally featured one, or occasionally two, manuals, while pedal-boards were rare. Higher-end pump organs offered a broader range of tones, and models intended for churches or affluent households were often housed in finely crafted cabinets.

Between the 1850s and the 1920s, several million reed organs and melodeons were manufactured in the United States and Canada, with some exported abroad. Major manufacturers included the Cable Piano Company, Estey Organ, and Mason & Hamlin.

In addition to the larger, furniture-sized instruments popular in the West, more compact designs also developed. The portable, hand-pumped Indian harmonium, adapted from Western designs such as the guide-chant in the 19th century, became a central instrument across the Indian subcontinent.