Angklung Simulator

The problem

Every angklung app I found online is a soundboard. You tap a picture of bamboo and hear a note. That copies the sound and misses the instrument. In an angklung ensemble, each player holds one or two notes. They spend most of a song waiting, watching a conductor signal numbers by hand. The coordination is the instrument, and nothing on the web lets you try it.

Two smaller gaps followed. The three playing techniques are usually taught as three sounds: kurulung (shake), centok (sharp pull) and tengkep (shake with one tube held). They are three ways of setting the same bamboo ringing. And on an accompaniment angklung, tengkep changes the chord. Four tubes sound a dominant seventh. Hold one with your little finger and it becomes a major triad. No simulator showed that.

What I built

Every note is computed from a model of a bamboo tube

I modelled each tube as a set of resonances that ring and fade, the way struck bamboo does. The site ships no audio files at all, and the build fails if one appears. A tube is closed at one end, so it has almost nothing at twice its main pitch. That gap makes the chord switch provable: the octave tube is the only source of that pitch, so holding it removes the note completely. The three techniques differ only in how the tube is struck. Centok is one hard hit, kurulung is a steady shake, and tengkep is the same shake with some tubes silenced.

The sound is measured by tests

I kept the sound engine free of any browser code, so it can render audio inside the test suite. Tests measure the pitch to within a few cents. They check that the held tube's note is gone under tengkep and present without it, and that centok makes exactly one strike. What you hear in the browser is the same audio the tests measured. Notes are timed against the audio clock itself, so a long piece never drifts.

The ensemble view shows who plays when

The main screen loads a melody, a set of angklung and a number of players. It shows who holds which notes and when each person comes in. Rests are drawn as empty space, because for an angklung player the waiting is the job. You can pick one player and play only that part, or mark players absent and watch the song break. When a song can't be shared out, the solver says why: a note is missing from the set, one player is needed twice at once, or there aren't enough players. It never trims the song to make it fit.

Cultural sources come with their limits

Padaeng is the diatonic-chromatic tuning Daeng Soetigna created in 1938. It ships beside two traditional tunings, salendro and pelog degung, as editable sets of intervals. Each one carries its source and a required note saying where the figure stops being verified. The salendro and pelog numbers are structural models, not measurements, and the build refuses to run if a note is missing. The site names Daeng Soetigna and Udjo Ngalagena on the page, and points to Saung Angklung Udjo and local ensembles.

Result

Angklung Simulator is live and public, in Indonesian and English. It has the rack of swaying angklung, the ensemble view, a technique lab that shows the strikes feeding the bamboo, the chord switch drawn as tubes, a side-by-side tuning comparison and a conductor lane. It also has a diagnostics page that reports how audio behaves on your phone. It runs on three runtime libraries and no audio or sound-processing library. I built it in about 37 hours over 12 and 13 August 2026.