How does a harmonium work?
Every note on a harmonium is a thin brass tongue buzzing through a slot, fed by air you pump with one hand. Take one apart in 3D, scrape a reed to tune it, pull the stops, hear why its fixed notes got it banned from All India Radio, and play it with your keyboard.
▶ Play with it · Read the 60-second explainer · Watch the 40-second video
- A box of reeds and a bellows. An Indian harmonium is a wooden box with a keyboard on top and a hinged bellows at the back. Inside sit a spring-loaded reservoir of air, a reed board with rows of brass reeds in little cells, a padded valve (a pallet) under every key, and stop knobs that choose which rows get air.
- A brass tongue that chops the air. Each note is a free reed: a thin brass tongue riveted over a slot. Air pushes it through, it springs back, and every swing lets out a puff. It swings at its natural frequency, f = 0.56·(t/L²)·√(E/12ρ), so a longer tongue is much lower. Makers tune by scraping: the tip to go up, the root to go down.
- Pump, store, squeeze. Your hand pushes air through a one-way valve into a reservoir held shut by springs. The springs keep the wind at about 0.5 to 1.5 kPa, only 1% above the room's pressure. Every open reed lets out about 0.07 L/s, so big chords drain it fast. Pump harder and it plays louder: that is its only volume control.
- Pull a stop, add a voice. Each stop opens a bank of reeds: bass an octave down, male at the key's pitch, female an octave up. Their harmonics stack and beat gently, and a musette bank tuned a few cents sharp beats a few times a second. Drone stops hold Sa and Pa without any key.
- Fixed notes in a sliding music. The reeds are tuned once, usually to equal temperament: Ga is 400 cents above Sa, while the pure 5/4 Ga that singers lean to is 386. Held together they beat about ten times a second. A scale changer slides the keyboard over the reeds to change key without changing fingers.
- From church organ to every stage in India. Missionaries brought pedal reed organs; in Calcutta, Dwarkanath Ghose is widely credited with the hand-pumped floor harmonium by 1875. It spread to bhajan, kirtan, qawwali, theatre and film. All India Radio banned it from 1 March 1940, and partly lifted the ban in 1971. Masters like Tulsidas Borkar made it a solo voice.
| Term | Meaning |
|---|---|
| Free reed | A springy tongue that swings freely through a slot, chopping airflow into puffs. Used in harmoniums, accordions, harmonicas and the sheng. |
| Natural frequency | The rate an object vibrates at by itself, set by its stiffness and its mass. |
| Cantilever | A beam fixed at one end and free at the other, like a diving board or a reed tongue. |
| Reservoir | The inner, spring-loaded bellows that stores air and keeps the wind pressure steady. |
| Pallet | The padded valve under each key that lets air through that key's reeds. |
| Stop | A knob that opens or closes the air to one bank of reeds, or to a drone reed. |
| Beats | The slow swell and fade when two nearly equal frequencies sound together. The beat rate is their difference. |
| Equal temperament | Tuning where every semitone is exactly 100 cents, so every key works but only octaves are pure. |
| Shruti | A fine step of pitch in Indian music, finer than a semitone; tradition counts 22 in an octave. |
More than 3,000 years from a Chinese mouth organ with tiny bamboo reeds, through the parlours and churches of Europe, to the hand-pumped box that sings with India's temples, gurdwaras, qawwalis and film songs.
- 1300 BCE · The sheng: the first free reeds (Musicians of Shang dynasty China, Northern China)
- 1780 · A machine that says its vowels (Christian Gottlieb Kratzenstein, St Petersburg, Russia)
- 1840 · The harmonium gets its name (Alexandre Debain, Paris, France)
- 1863 · Scientists tune harmoniums to pure intervals (Hermann von Helmholtz; Robert Bosanquet, Heidelberg, Germany, and London, England)
- 1875 · The hand-pumped harmonium (Dwarkanath Ghose (Dwarkin & Son), Lower Chitpur Road, Kolkata (Calcutta), India)
- 1912 · The bane of Indian music (Rabindranath Tagore, Bengal, India)
- 1940 · All India Radio bans the harmonium (Lionel Fielden, Controller of Broadcasting, after a campaign by John Foulds, Delhi, India)
- 1971 · The ban is partly lifted (All India Radio and the Sangeet Natak Akademi, New Delhi, India)
The full story, with 29 moments, charts, people and 58 sources: glassbox.how/e/harmoniumclear/history. The data lives in history.json.
Made with the Glassbox studio from this box's storyboard (window.glassbox.director). Free to reuse under CC BY 4.0.
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|---|---|---|
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