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You can play different songs on the piano in Tifa's room in Nibelheim.

[edit] How to play the piano

You have one octave to play with. The notes are as follows.

Note	Button	PC	PlayStation
Do	[Cancel]	0/Ins
Re	[Switch]	./Del
Mi	[Menu]	+
Fa	[OK]	Enter
So	*[Cancel]	9+0/Ins	+
La	*[Switch]	9+./Del	+
Ti	*[Menu]	9++	+
Do'	*[OK]	9+Enter	+

Asterisked entries mean you need to press either [PgUp] or [PgDn] while pressing the button in question. Therefore, either 9 or 3 on PC or or on PlayStation work.

You can also play three different chords.

Chord	Button
C	Down
F	Left
G	Up
C'	Right

If you play all the notes in order (as in on the list that comes up, you receive tifa's secret savings, a mighty 1 gil.

Playing piano is ended by pressing [Start] (5 on PC, on PlayStation).

[edit] Songs to try

So far, see Tifa's limit break on information on how to play the Highwind theme.