Looking For A Good Text

Obviously, its got to be a Tolkien songs from Lord of the Rings!

That would be almost good, but the copyright would be a problem here. Something in public domain would be way simple to use^^

 The sonata structure was already severely altered in Beethoven's era, 

I would dispute this. Beethoven was responsible for significant innovations, but they were all evolutionary. His last works were just as much sonatas as say Haydn's early works. It was the generation of Romantic composers that came after who trashed sonatas, by deemphasizing form over emotional expression.

in the end of the day there aren't that many standarts and rules in music. follow what you think is best.

Christian, I'm guessing you haven't considered alternate sources such as speeches by Winston Churchill or other historical documents, even those divorced from liturgy. Public service announcements, traffic announcements, courtroom transcripts of high profile cases, weather reports, declarations and deceptions by tyrants of old and new (yes I mean Obama), or this work by Johann Johannsson, the text being the reading of a technical manual from the IBM archives. All these things are source material and with skill could transcend their origins. Which is the point.

https://www.youtube.com/watch?v=KPFAkBCizr8

Set to music the words of the announcer for a world cup game. Then call it a requiem (if the text goes on for too long, you can always spin off portions of the game into a Magnificat, Nunc Dimittis, etc).

Other texts to try: TV commercials, personal ads in the newspaper, graffiti, YouTube comments, field recordings of conversations between random people, the phone book.

Also try running a text through a few random languages in Google Translate until it turns into poetry. Here's an example:

(French -> Latin -> Russian -> Norwegian -> Hebrew -> Finnish -> Slovenian -> English)

Deutsche Grammophon yellow Li superiority of a classic ... but more or less, and every music lover discophile shows that reason, established in 1898 to improve the transparency Emil Berlin "gramophone" Edison's phonograph. For many years, the chin and the German Deutsche Grammophon themselves, depending on the clerk and was the first that addresses a wide Caruso, in 1902 the Russian bass Saljapin in his life, partly as a result. In 1941, the company acquired Siemens, Berlin, and so it was that after the victory, he destroyed his freedom of art as a whole.

Ok, so I'm using the good old Requiem text. Here it is: http://www.youngcomposers.com/music/listen/6568/Requiem%20(1%20-%20Introitus)