Classical music, I believe has to be the most structured form of art there is. The great composers, such as Haydn, Bach, Mozart, and Beethoven, all wrote in specific forms. The sonata, fugue and even the symphony are all carefully laid out in terms of requirements. The fugue, for example, is one of the most difficult pieces to compose with all the rules that must be met. Yet these composers, Bach especially, were able to shine and produce some wonderful music. Was creativity hampered by these rules? I don't think so. For more information on fugue structure go here. I believe that much of this great music would not be here if it weren't for these musical structures. The sonata is a longer piece, yet still perfectly formed with the Exposition, Development, and Recapitulation sections. These men knew their constraints exactly, and stayed within them. Beethoven, in his later life, varied from these forms, but then still adhered to his own new rules.
We can also see a similar set of restraints in jazz. Jazz pieces are not usually very scripted and can sometimes be mostly improvisation. The creativity shown by these improv artists is amazing. They must still follow the rules of the key that they are playing in, or it will not sound good at all. Jazz improv is the best and most creative when restrictions are adhered to.
I have included some pieces of music that I like. You will find Sonatas, Fugues, as well as some other pieces.
Now for the music!
The songs are:
1. Bach - Toccata and Fugue in D
Minor
2. Bach - Fugue 17 Book 1, The Well Tempered Clavier
3. Beethoven - Moonlight Sonata, Quasi Una Fantasia
4. Beethoven - Sonata in A Op. 6
5. Bach - Cello Suite 3 in C
6. Telemann - Quartet in Eb
7. Mozart - Sonata (Not sure which)
8. Mozart - Ode To Joy