Maracas, tambourine and shakers online

On an iPhone, motion access is yours to grant, and the browser only accepts that request from inside a tap on the page. Your first tap on the instrument is what asks; if you dismissed the prompt, reload the page and tap again. Once the sensor is running, a “Motion sensor is working” mark appears under the instrument. If motion is blocked for the site in your settings, or the sensor does not respond, the same place says so, and tapping and dragging with a finger keep playing the same instrument.

They are two different gestures. In a shake the beads have to travel: your stroke throws them, and they sound when they reach the far wall, 20–80 ms later depending on the size of the shell and the force of the stroke. A real maraca does exactly this, which is why players lead the beat. In a tap the shell itself hits the beads lying on its wall; they have nowhere to fly, so the sound starts immediately. The flight time of the current instrument is shown under it; a smaller shell means a shorter flight.

Each has its own gesture. The guiro is played by dragging the stick along the ridges: the speed of your hand sets the pitch of the rasp, and a long stroke one way with a short one back gives its familiar pattern. On the cabasa, drag sideways and the chain of steel beads turns over the ribbed cylinder. Turn the rainstick: the grains pour for as long as it is tilted, and once they have all run through you turn it over. With the phone in your hand, the guiro answers a sweep forward and back, the cabasa a twist around the long edge, and the rainstick a tilt.

Because the beads fall. Going down, gravity helps, and they arrive sooner and tighter; going up they fight gravity and arrive later and softer. Real shaker recordings differ in the same way, which is why sample libraries record the up-stroke and the down-stroke as separate files. On the keyboard these are the up and down arrows; on a phone it is the direction of your stroke.

No, nothing here is played back. The statistics of the collisions inside a burst come from Perry Cook’s PhISEM model, whose resonances and decay rates were fitted to measurements of real maracas, cabasas, tambourines and sleigh bells; the mechanics of the bead cloud, the rasp of the guiro and the hit on the tambourine head are computed here as well. Real recordings are used for checking: on public-domain shaker recordings the number of bursts and the gap between collisions were measured, and the model is held to those numbers by a test.

It asks the simulation. The instant the bead cloud hits the wall is an event known to the audio sample, so the number shown is the distance from the metronome click to the sound you heard, not to the moment you moved your hand. While “Play itself” is on, the readout stays silent: your note cannot be told apart from the groove’s.

Yes. A click on the instrument is a strike and a mouse drag is a shake: the force comes from the size and speed of the movement. The space bar strikes, holding it gives a roll, the left and right arrows play the left and right hand, up and down play up-strokes and down-strokes, and the digits 1–9 switch instruments. The keys work while the instrument has focus, that is, after you click it.