Source of MP3: http://www.pico-score.com/
Played by: Pico & TAM
Wallpaper by Felesya.
Update: How to download the .mp3
1. Go to http://www.pico-score.com/
2. Second box from the top on the leftmost side of the page, click it.
3. It should bring up a new page with CLANNAD near the top. 5th row down, it should say, "ひぐらしのなく頃に" with a red character. Click it.
4. Look for the "You" song by Dai, it should be the first one. Click the grey(?) dot/circle under the two stars.
5. A new page, with piano sheet music appears. Right-click & save the link to the right of the link that says MP3. It's in the green-ish/teal color.
6. Enjoy.
UPDATE:
http://www.mediafire.com/?cs347p6dzq4psbt
Here's a link to the .mp3. The one from the website was taken down for some reason.
Home » プレイリスト » Youtube » 「Higurashi no Naku Koro ni」 - You (Piano & Violin Instrumental)