I really search the Zelda Hyrule Field (In Zelda Ocarina of Time) for piano but i don't find him.

Hyrule Field (piano) can be found here:

http://members.home.nl/nintendosheetmusic/

You'll need Finale (Notepad) to view the sheet music, if you don't have it already,which can be downloaded here:

http://www.finalemusic.com/notepad/