Notes fall down the middle of the field toward the line above the keyboard. Each tile tells you what to play: a letter, an interval, a number, a chord, or a Nashville numeral depending on the level. A single note falls straight above the key you need until a free run's score passes double what cleared the level, when it moves to the middle of the field as a harder reward; a chord always falls above its own keys.
Hit the right key while the tile is near the line. Closer to dead-on earns PERFECT, a little early or late earns GOOD or OK, and missing the window or hitting the wrong key breaks your combo. The timing window widens as the tiles speed up, so a faster level asks you to read quicker rather than to have quicker reflexes than a human being has.
A chord is different. It falls as its own notes, one tile per note, each above the key it belongs to and under a bracket carrying the chord's name, so you watch C E G B come down in the shape of the chord and light up gold as you land them. It is live from the moment it appears, so you have the whole descent, and it falls slower than a single note in the same level: the more notes it wants, the slower it comes.
Every key on the piano carries its real name. White keys read C D E F G A B. Black keys carry both of theirs: the sharp name on top, the flat name underneath, because one black key answers to two names.
Play with a mouse or a finger. On a computer you can also use the keyboard row A S D F G H J for the white keys and W E, T Y U for the black keys above them.
Getting to the end of a level is passing it. A run ends on misses: twenty of them on the first three levels, fifteen through level 6, ten from there up. Surviving thirty tiles keeps you above the bar, so if you reach the end of a level you have cleared it. Then the field freezes, the score banks, the next level opens, and you choose: move on, or keep going on the same run with no tile limit at all.
A level opens a fifth under its speed and finishes a seventh over it, so the first few tiles are a gift and the last few are not. The first four rungs of the ladder climb 8% each and every rung after that climbs 14%, and that never stops or levels off.
On a phone the game gives you room. Every timing window is a third wider on a touchscreen than on a mouse, the first three levels hold the field to two tiles at a time so you are never tracking a crowd, and the timing windows on the levels being learned are wider still, closing back to normal by level 11.
In a free run, once your score is double what you cleared the level with, the single notes stop falling above their keys and drop from the middle of the field instead. At that point you have to know where a note lives rather than watch a column. Chords never move: their notes fall above the keys they belong to, which is the whole point of them.
Fourteen levels teach the theory; after that the ladder runs forever. Four things climb together and none of them stop: the tiles fall faster, they come more often, from level 5 up the gap between them stops being regular, and from level 8 up they stop sharing a single speed, so they drift apart and overtake each other. Every level remembers its own high score, and Level 6 remembers roots and full chords separately.
Sound: tap anywhere once when the page opens. Phones will not make sound until you touch the screen, and on an iPhone the ringer switch has to be off silent.