04 (orchestral) - First part is the Blue danube walz by J. Strauss II, then there's a little bit of the Waltz of the Flowers from the Nutcraker (Tchaikovsky)
09 (choral) - That's the Donna Nobis Pacem part of some mass setting - I don't know which one
14 (orchestral) - Dvorak, Symphony no. 9 - III. Scherzo, molto vivace
16 (choral) That's Fin ch'han dal vino, an aria from mozart's opera Don Giovanni
18 (strings) Duuhhh wait. La ronde des lutins
20 (choral) Mozart - Vesperae solennes de confessore, K. 339 - V. Laudate Dominum
And that's all I can help you with!
EDIT: Omg Manuel :P you posted while i was writing mine