MIDI notes are matched exactly, octave included. Middle C is MIDI note 60 on every keyboard, though some keyboards label it C3. When you play the right letter in the wrong octave, the game tells you to play it higher or lower. Bass notes are played in the middle of the keyboard, one octave above where they are written, so you don't need the very low keys. If your keyboard has an octave or transpose button, set it to zero.

Yes. Any class-compliant USB MIDI keyboard that your iPhone or iPad can see works. Older keyboards with only 5-pin MIDI sockets need a USB MIDI interface cable and a camera or USB adapter.

Microphone mode is approximate. Play in a quiet room, with the device near the instrument, and turn the game's sound effects down. Some keyboard sounds sit an octave above or below the key you press. Tap the OCT button at the top of the game to shift what the microphone hears by one octave. Background music pauses while the microphone is on.

Treble and bass are separate on iPhone because there isn't room for two staves and the keyboard. Both clefs together is available on iPad.

No. Sessions are practice: nothing is saved to your high scores or Game Center.

Changing clef on the start screen resets a saved game for that clef, so each clef keeps its own game. Use Restart on the start screen to begin again.