A harmonium is a free-standing keyboard instrument similar to a reed organ. Sound is produced by air, supplied by foot-operated or hand-operated bellows, being blown through sets of free reeds, resulting in a sound similar to that of an accordion.
During the mid-19th century missionaries brought French-made hand-pumped harmoniums to India. The instrument quickly became popular there: it was portable, reliable and easy to learn. It has remained popular to the present day, and the harmonium remains an important instrument in many genres of Indian music. It is commonly found in Indian homes. Though derived from the designs developed in France, the harmonium was developed further in India in unique ways, such as the addition of drone stops and a scale changing mechanism.
A popular usage is by followers of various Hindu and Sikh faiths, who use it in the devotional singing of prayers, called bhajan or kirtan. There will be at least one harmonium in any mandir (Hindu temple) or gurdwara (Sikh temple) around the world. The harmonium is also commonly accompanied by the tabla as well as a dholak. To Sikhs the harmonium is known as the vaja/baja. It is also referred to as a “Peti” ( A loose reference to a “Box”) in some parts of North India and Maharashtra.
The harmonium plays an integral part in Qawwali music. Almost all Qawwals use the harmonium as their sole musical accompaniment. It has received international fame as the genre of Qawwali music has been popularized by renowned Pakistani musicians such as Nusrat Fateh Ali Khan.
Harmoniums consist of banks of brass reeds (metal tongues which vibrate when air flows over them), a pumping apparatus, stops for drones (some models feature a stop which causes a form of vibrato), and a keyboard. The harmonium’s timbre, despite its similarity to the accordion’s, is actually produced in a critically different way. Instead of the bellows causing a direct flow of air over the reeds, an external feeder bellows inflates an internal reservoir bellows inside the harmonium from which air escapes to vibrate the reeds. This design is similar to bagpipes as it allows the harmonium to create a continuously sustained sound. (Some better-class harmoniums of the 19th and early 20th centuries incorporated an “expression stop” which bypassed the reservoir, allowing a skilled player to regulate the strength of the air-flow directly from the pedal-operated bellows and so to achieve a certain amount of direct control over dynamics.) If a harmonium has two sets of reeds, it’s possible that the second set of reeds (either tuned unison or an octave lower) can be activated by a stop, which means each key pressed will play two reeds. Professional harmoniums feature a third set of reeds, either tuned an octave higher or in unison to the middle reed. This overall makes the sound fuller. In addition, many harmoniums feature an octave coupler, a mechanical linkage that opens a valve for a note an octave above or below the note being played, and a scale changing mechanism, which allows one to play in various keys while fingering the keys of one scale.
Harmoniums are made with 1, 2, 3 and occasionally 4 sets of reeds. Classical instrumentalists usually use 1-reed harmoniums, while a musician who plays for a qawaali (Islamic devotional singing) usually uses a 3-reed harmonium.