A digital-waveguide model of four stiff strings. Each string has a distributed one-sided contact barrier (the jawari bridge with its thread), a frequency-dependent loss filter, a dispersion all-pass for bending stiffness, and a modal resonator bank for the gourd body. The output is rendered offline at an oversampled rate and played back, with an averaged spectrum, a spectrogram and a harmonic table.
What it is. A physics-based tanpura simulator. Nothing is sampled: the sound is computed from the strings' material, thickness and tension, the shape of the jawari bridge and thread, and the resonances of the gourd. Everything runs in your browser. Nothing is uploaded and no data is collected.
Quick start.
Good things to try. Move the thread position in small steps (18, 19, 20 mm) and listen to the buzz open and close. Compare Traditional gourd, Fiberglass gourd and Gourd removed. Untick Enable jawari to hear a plain string drone.
Tips. On a phone or an older computer, set Oversampling to 2× for faster renders. On an iPhone, turn the silent switch off or you will hear nothing. The body resonances are illustrative, not measurements of a particular instrument.
| Material | ⌀ mm | ΔT % | Gain |
|---|
| String | f (Hz) | μ (g/m) | T (N) | % break | B |
|---|
Tension is the value needed to reach the selected pitch (T = μ(2Lf)²). ΔT changes it, which detunes the string (f ∝ √T) and changes the inharmonicity B = π³Ed⁴ / (64TL²). Small ΔT differences between the two Sa strings give the natural beating.
Without a thread, the string leaves the bridge tangentially at its back edge (x = 0), and the bridge surface falls away by gs(x) = drop·(x/length)p. The thread lifts the string only by e = thickness − gs(thread position), pivoting at the edge. The jawari "opens" when e is close to 0, because the string then grazes the bridge over several millimetres. That is why tiny thread movements matter so much. A larger e means less contact, a cleaner and duller tone, and eventually a sitar-like click or no buzz at all. A flatter profile (larger p) widens the grazing zone. Restitution ε = 1 is a lossless (elastic) contact and ε = 0 a fully absorbing one.
The body mode frequencies, Q values and gains are illustrative, not measurements. To match a specific instrument, replace them with modes measured on it (for example from a tap test) in GOURDS in the source.
Oversampling sets the spatial resolution Δx on the bridge. At 4× the contact zone gets about 10–30 waveguide points. Use 8× for the finest bridge detail, at the cost of a slower render.
Ticks along the top mark the harmonics of the low (kharaj) Sa. Levels are relative because every render is normalised to the same peak, so compare spectral shapes, not absolute dB.
The jawari shows up as a band of strong overtones that sweeps downward through each note's decay. This is the "formant sweep" that gives the tanpura its live, shimmering sound. Turn the jawari off to hear and see it disappear.