Here's what you should hear:
DAY 1: Bach's Invention in C Major in the R.H.|
DAY 2: Mozart's "Là ci darem la mano" in the L.H.
(Giovanni/Zerlina duet from Don Giovanni)
DAY 3: Brahms' Waltz No.15 in A-Flat, Op.39
DAY 4: Vivaldi's "Spring" from The Four Seasons in the R.H.
DAY 5: Beethoven's Symphony No. 5
DAY 6: Schubert's accompaniment to the song, Erlkönig
(Yes, in the original the notes are marked as triplets, but they can just as easily be heard as sextuplets. Let's call them sextuplets.)
DAY 7: Stravinsky's The Rite of Spring, "Dance of the Youths and Maidens"
(not necessarily notated in 7/8, but features many asymetrical accents)
DAY 8: Tchaikovsky's Piano Concerto No. 1, famous octave passage from finale
(This day gave me the most trouble. An earlier posted version of this card featured the famous opening piano chords from the 1st movement of this concerto. An even earlier version featured the Scherzo theme from Mendelssohn's Octet.)
DAY 9: Wagner's "Ride of the Valkyries" from Die Walküre
(Yes, there are nine Valkyries.)
DAY 10: Chopin's Etude in A-flat, Op. 25, No.1
(Yes, Chopin really had only ten fingers; sometimes it seems more are needed.)
DAY 11: I made this one up, but Charles Ives certainly wrote more than one 11-note cluster in his life.
(Some of his piano works call for the pianist to hit as many notes as possible with a block of wood!)
DAY 12: I also made this music up, although I did carefully construct a 12-tone row of which Schoenberg would be proud.
(The row is in the R.H., with its retrograde in a series of three-note chords in the L.H. I'm sure you noticed that.)