About this rack

Excite / Resonate is an encyclopedia of sixteen instruments built around one idea from acoustics: almost every instrument is an exciter that pushes, a resonator that rings at a set of frequencies, and often a body that hands the vibration to the air. The rack lets you take those apart and wire them back together in combinations nobody builds.

How the sounds are made

Nothing here is a recording. Each note is synthesised in your browser by modal synthesis: the resonator is a list of modes (frequency ratios, strengths and decay times), the exciter decides how hard each mode is driven and for how long, and the body is a set of broad resonance peaks that lift some frequencies and not others. A plucked or struck note is a set of decaying sine waves; a bowed, blown or buzzed note is held while you hold the plate, with a little noise for rosin, breath or reed.

The mode ratios come from published measurements where they exist: drumheads (Bessel zeros), timpani (Benade's measured 1 : 1.50 : 1.74 : 2.00 : 2.25 : 2.49), marimba bars tuned 1 : 4 : 10, church bells at 0.5 : 1 : 1.2 : 1.5 : 2, steelpan notes at 1 : 2 : 3, and Raman's near-harmonic tabla. Body peaks are rounded from the usual textbook values. This is a sketch of each instrument's physics, not a sampled instrument: the clarinet will not fool a clarinettist.

How the sand figures are made

In 1787 Ernst Chladni bowed sand-covered metal plates and drew the patterns the sand made; he showed them to Napoleon in 1809. The grains bounce off everything that moves and come to rest along the nodal lines, where the plate stays still. Luthiers still check violin plates this way.

On this rack each grain is bounced in proportion to how much the plate moves where it lies, and slides downhill towards the still lines. The figures for drums are true modes of a round membrane fixed at its rim. For every other instrument the figure is a mode of a square plate clamped at its centre, chosen by the note you play: it shows what nodal lines look like, not the actual vibration of a violin or a bell. When the note dies away, the sand slides back into the drawing of the instrument.

Facts and pictures

Dates, dimensions and acoustics were gathered in October 2026 from museum and university sources, among them the Metropolitan Museum of Art, the University of New South Wales music acoustics pages, HyperPhysics, Britannica, the Keltek Trust and C. V. Raman's papers, and checked against Wikipedia. Where historians or physicists disagree, the page says so in its "Often said" box rather than picking a side. Instrument classes follow the Hornbostel–Sachs system.

Every sand drawing was drawn in code for this site. The photographs come from Wikimedia Commons and are credited under each one with their licence.

Whyarium

This is encyclopedia no. 43 of Whyarium, a set of fifty small encyclopedias, each with its own way of showing how something works. No ads, no tracking, no accounts.