EtherpadHow Etherpad sings.
There are no recordings inside Etherpad. Every note is synthesized the instant you touch the surface, by Csound — a sound-programming language trusted by composers and researchers since 1986. This is the journey from fingertip to ether.
First, what is sound?
Four ideas explain nearly all of synthesis. Master these and the rest of this page — and most synthesizers ever built — will make sense.
Sound is moving air
Anything that vibrates pushes air in waves. How fast it vibrates is the pitch — faster means higher. How far it swings is the loudness. Everything you hear is just these two numbers, dancing.
An oscillator is a shape on repeat
Draw one tiny wave shape and replay it hundreds of times per second — like a music box cylinder spinning. The shape sets the character: sine is pure, triangle is soft, sawtooth is bright, square is hollow.
FM — waves bending waves
Frequency modulation: one wave wobbles another wave's pitch thousands of times a second. Out come shimmering metallic overtones no single wave could make — the secret behind Etherpad's bells and its signature pad.
The envelope gives it life
Real sounds are born and they die: a bell strikes then rings away, a pad blooms slowly. The envelope shapes a note's loudness over time — attack, sustain, release. It is why lifting your finger fades the note like a breath instead of cutting it dead.
From touch to tone
Your finger becomes data
The app writes each fingertip's position to named channels — touch.0.x, touch.0.y — like order tickets passed through a kitchen window. The engine reads them live, and every touch gets its own independent voice.
Movement is smoothed
Raw touch positions jump in steps that would click and zipper. A portamento opcode glides every value toward its target in ~10 milliseconds — the reason Etherpad feels liquid instead of steppy.
Position snaps to music
Your X position is mapped onto a scale table — a list of semitone steps like 0, 2, 4, 7, 9 — then snapped to the nearest step and converted to a frequency. That's why you can't play a wrong note: the grid is the key.
A voice is synthesized
The chosen sound builds the waveform live at that frequency: FM synthesis for bells and the Ether Pad, band-limited analog-style oscillators for saws and triangles, vowel filters for the choir. Y controls loudness and timbre together — higher is brighter, louder, more alive.
The signal path
Voices never reach the speakers directly. Like a recording studio, everything flows through shared mixing buses — and the effects are what make it ethereal.
Why it sounds ethereal
Three ingredients. A reverb with an unusually long tail keeps every note ringing after you lift your finger, like a clap in a cathedral. A feedback delay repeats each phrase softly, like a voice across a canyon — old notes linger underneath new ones. And portamento everywhere means nothing ever jumps — pitch, volume, and tone all glide. Music made of curves, not corners.
Learn it, build it
The whole engine is open source, and it descends from the Csound MultiTouchXY example by Steven Yi and Victor Lazzarini, built into an instrument by Paul Batchelor. Go deeper: