You can play different songs on the piano in Tifa's room in Nibelheim.
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).
Songs to try
So far, see Tifa's limit break on information on how to play the Highwind theme.