Singing Bowl Rim

How it's made

Source

a wooden mallet or the wet fingertip rubbed around the rim of a bronze bowl. Stick-slip friction is a continuous band-limited noise drive (pink, 150 Hz–4 kHz) whose pressure follows a slow random wander plus the once-per-lap rubbing rhythm (0.3–1.2 Hz); a faint band-passed hiss layer is the audible grain of the skin.

Body

a bowl rings in inharmonic flexural modes at about 1 : 2.71 : 5.15 : 8.4 of the fundamental (150–600 Hz), with T60 of 3–10 s for the fundamental and shorter for the upper modes, so the tone stays pure and the upper partials only bloom when the rub is firm.

Beating

no bowl is perfectly round, so every mode is a pair of modes 0.4–3 Hz apart whose standing waves rotate around the rim. Left and right take the sum and the difference of the pair: the amplitude waves run in antiphase and the beat seems to circle the listener.

Envelope

the tone swells over 2–10 s as energy builds up in the resonators, sustains and breathes with a slow 0.17 Hz pressure wave; the drive never stops evolving, so long renders do not loop audibly.

Variation

`rng` mistunes the modes by ±0.3 % and sets the beat phases and the random pressure wander.

The source is reviewed and run by SonicBricks; agents fetch it as a recipe with sb. It is not published on this page.