Here is a compilation of all the music presented in Piano no Mori thus far. For a master list organized by composer, click here.

Kai's Childhood

The Little Brown Jug by Joseph Winner
  Arranged by Ajino. Kai points out two mistakes that Ajino makes, having only heard the piece once before. This leads Ajino to discover his talent. Later, Kai plays the piece for Shuuhei when they go together to the "piano in the forest."
Radio exercises
  Background music to daily exercises on the radio. Kai plays it by ear in a jazzy arrangement at Shuuhei's house, where the whole family agrees that his piano playing is more like a machine gun than music. He plays it for Shuuhei later at the "piano in the forest" and it sounds more normal.
Mozart Sonata in F Major, K.280
[mvt i, ii, iii]
  Required piece for the preliminaries of Japanís 56th National Piano Competition. Shuuhei performs the piece for Kai, who remembers it after just hearing it once.
Beethoven For Elise, Symphony No.5 in C Minor ("Fate"), Mendelssohn Wedding March
  Pieces that Ajino plays for Kai.
Chopin's Minute Waltz
  Piece that Ajino plays for Kai. Kai has trouble playing it on the piano in the forest, probably the biggest shock of his younger years. Ajino tells him that playing Chopin requires a certain flexibility and dexterity of the fingers that cannot be achieved through sheer force.
Dvorak Symphony No.9 in E Minor ("New World")
  Arranged by cellist Takadaba in a Eurobeat style. Kai plays it perfectly the first time he sees it on the road, and subsequently joins the street performers as a part-time job and improving tremendously.

Later Years

Bach English Suite No.2, Liszt Funeral March
  Kai plays these pieces in P Club, under the guise of "Maria." He plays them as accompaniment to stripping. Takeshi remarks that this is sacrilege unto classical music, and Shuuhei remarks that 'the pieces seem to be made for this express purpose.'
Hanon Arpeggios
  Kai practices these very softly in an attempt to master the pianissimo.
Liszt La Campanella
  Kai plays this for Shuuhei after five years of being apart. Shuuhei is overwhelmed by how much he has improved.