FluteClear

How does a flute work?
Nothing inside a flute moves: a jet of breath flips in and out across a sharp edge and the air in the tube does the singing. Play a bamboo bansuri and a silver concert flute in 3D, cover the holes, and blow hard enough to jump an octave.

▶ Play with it  ·  Read the 60-second explainer  ·  Watch the 40-second video

In 60 seconds

1. A tube, a hole and some fingers. A bansuri is a bamboo tube with a cork at the top, a hole to blow across and six burnt finger holes. A concert flute is the same idea in silver, in three joints, with Theobald Boehm's padded keys to close holes too big and far apart for bare fingers.
2. A reed made of air. You blow across the hole, not into it. The thin jet of breath hits the far edge and flips in and out of the tube hundreds of times a second, in step with the air inside. Nothing solid vibrates: the jet is an air reed. Its speed comes from your mouth pressure, U = √(2p/ρ).
3. The air column sets the note. A flute is open at both ends, so its air rings with a pressure node at each end and half a wavelength along the tube: f = v/2L, plus small end corrections. It also rings at 2f, 3f and 4f. A clarinet, closed at one end, only has the odd ones and sounds an octave lower.
4. Open a hole, shorten the tube. An open finger hole lets the wave out, so the pipe acts as if it ends just past the hole and the note rises. A smaller or half-covered hole lets less out, so the note sits lower: bansuri players use half-holes for komal notes and slides.
5. Blow harder, jump an octave. The jet has to cross the hole in the right time for a mode. Blow faster, or bring your lips closer to the edge, and the flute jumps to its second mode, an octave up, then to a twelfth and two octaves. That is how six holes cover more than two octaves.
6. Bamboo, ragas and keys. A bansuri is named by its Sa, with the top three holes closed. Pannalal Ghosh made the long bansuri a concert instrument and Hariprasad Chaurasia took it round the world. Its music lives between the notes, in meend and gamak. Boehm's keys of 1847 took the other road: a clean chromatic scale.

Words worth knowing

Term	Meaning
Air reed	A jet of breath that flips in and out across a sharp edge, doing the job a cane reed does in a clarinet.
Embouchure hole	The hole a flute player blows across. The breath splits on its far edge.
Standing wave	A wave that seems to stand still in the tube, with nodes where the pressure never changes.
Open–open pipe	A tube open at both ends. Its lowest note is f = v/2L, and it has every harmonic: 2f, 3f, 4f.
End correction	The extra length a pipe seems to have because the vibrating air pokes a little way out of each open end.
Overblowing	Blowing harder with the same fingering so the tube jumps to a higher mode, often an octave up.
Half-holing	Partly covering a finger hole to bend a note down in between, used for komal notes and meend.
Boehm system	Theobald Boehm's 1847 flute: large holes placed for good tuning, closed by linked, padded keys.
Sa	The home note of Indian music. A bansuri is named by its Sa, played with the top three holes closed.

A short history

More than 40,000 years from a hollow bird bone with finger holes to silver flutes and bamboo bansuris on concert stages around the world.

• 41000 BCE · The oldest flutes we are sure of (Early modern humans (Aurignacian culture), Geissenklösterle cave, Swabian Jura, Germany)
• 7000 BCE · Crane-bone flutes that still play (Early farmers of the Jiahu culture; studied by Zhang Juzhong and colleagues, Jiahu, Henan province, China)
• 433 BCE · The oldest surviving side-blown flute (Musicians of Marquis Yi of Zeng, Suizhou, Hubei province, China)
• 900 · Krishna's flute (Authors of the Bhagavata Purana, India)
• 1680 · The one-keyed Baroque flute (The Hotteterre family of instrument makers, Paris, France)
• 1752 · Quantz writes the great flute guide (Johann Joachim Quantz, Berlin, Prussia)
• 1847 · The modern flute is born (Theobald Boehm, with Karl von Schafhäutl, Munich, Bavaria)
• 1940 · The bansuri goes to the concert hall (Pannalal Ghosh, Bengal and Bombay (Mumbai), India)

The full story, with 28 moments, charts, people and 61 sources: glassbox.how/e/fluteclear/history. The data lives in history.json.

Video and slides

Made with the Glassbox studio from this box's storyboard (window.glassbox.director). Free to reuse under CC BY 4.0.

File	What	Size
glassbox/reel.mp4	Reel / Short, with captions and soundtrack	1080×1920
glassbox/video.mp4	YouTube video, with captions and soundtrack	1920×1080
glassbox/slide-1…10.jpg	Instagram carousel	1080×1350
glassbox/thumb.jpg	YouTube thumbnail	1280×720
glassbox/cover.jpg	Share card and repo social preview	1200×630
glassbox/history-reel.mp4	“History in 10 moments” Reel / Short	1080×1920
glassbox/history-slide-*.jpg	History carousel	1080×1350
glassbox/post.json	Post copy and schedule used by the publish kit

Privacy

This box has no accounts and no ads, and it ships its own fonts and libraries. When you run it yourself it sends nothing anywhere. On glassbox.how, the site's /bar.js also loads Glassbox's analytics: Google Analytics to count visits (it asks first in the EU, UK and Switzerland, and stays off when your browser sends Global Privacy Control or Do Not Track) and ClickTrust to detect bots.

It remembers a few things in your own browser only, and never sends them anywhere:

Browser storage key	What it holds
fluteclear.v1	Which chapters you have opened, your best quiz scores, and sound on or off.

Exactly what each one sees is at glassbox.how/privacy.

Licences

• Code: MIT. Use it, change it, ship it.
• Explanations, text, images and videos (glassbox.json, glassbox/): CC BY 4.0. Credit “Glassbox, glassbox.how/e/fluteclear”.
• Third-party parts keep their own licences: three.js (MIT), Geist, Instrument Serif (SIL OFL 1.1).
• The Glassbox name and logo aren't covered by either licence. See the terms.

Found a mistake? Open an issue. Corrections happen in public.

Run it

It's plain HTML, CSS and JavaScript. No build step and no dependencies. Run locally, it contacts no other website.

python3 -m http.server 8000

Three.js and the fonts ship in vendor/ and fonts/, so it also works offline.

Then open http://localhost:8000.

How it's built

File	What
index.html, css/app.css	The page and its styles
js/app.js, js/stage.js, js/ui.js, js/kit.js	The shared Glassbox 3D engine: chapters, 3D stage, controls, quiz, video director
js/chapters/*.js	One file per chapter: the 3D model, controls, text, key terms, quiz and video scenes
js/flute.js	The shared flute physics and parts: speed of sound, a tone-hole model that places the holes, the jet that picks the mode, a WebAudio flute voice, keyboard input, and 3D models of a bansuri and a Boehm concert flute
glassbox.json	Title, question, explainer beats, key terms, browser storage and credits shown on glassbox.how
reel in each chapter	The storyboard the Glassbox studio records into short videos
glassbox/	The published video, slides, thumbnail and post copy
fonts/, vendor/three/	Self-hosted Geist and Instrument Serif (SIL OFL 1.1) and three.js (MIT)