The discrete event-based nature of granular synthesis suggested the rainfall metaphor used in the device, which then indicated a watering can as an appropriate controller.
Droplets are produced at a rate that depends on the tilt angle of the watering can and have an appropriate initial velocity.
This is done by tilting the watering can while holding the palette below.
It is not required for experienced players as the metaphor provides an understanding of how the water flows from the watering can.
Both player and audience can imagine the arc of water sprinkling from the watering can and intersecting the palette.
I nearly went crazy during last year's dry summer—the loneliness of the long-distance runner with a watering can!
If, say, a common, simple watering can was being used, nobody would get excited about that.
He carries with him an appropriately shaped shovel and a watering can.