Sheet music
The letters are the keys. Type them here and the page sounds, exactly as the water does — so you can learn a phrase without leaving the page it belongs to.
Nothing here is keeping score. There is no timing to hit and no wrong note; these are somewhere to start, not a test. The pool is five notes that always agree, which is why so much of it sounds deliberate however you play it.
The whole keyboard
Fifteen notes, low to high. Each row is an octave; left to right within a row goes up the scale, and further right also sounds brighter.