Okay, I've got this done, sort of. Wasn't very hard.
http://www.geocities.com/spotandsmudge/OOT_Chamber_of_Sages_pre.midCheck that out, and you might want to compare it to the original. The instruments and volume levels sound near-perfect to me, but MIDI sounds differ with sound cards. So let me know if it needs urgent changes.
Also, it's not looped. I don't have the OST handy anymore so I don't know how many times it loops or when it fades out, "officially" speaking. If you could, tell me how many times you want it looped and what kind of fade you'd like.
I've been trying to learn MIDI loop points forever and still can't do it. If anybody out there knows how, this song should loop from beat 47 to 19.
Will re-upload when it's finalized.
[edit]
Upon re-listening, I think I varied the expression too much on the piano tracks. It's supposed to get slightly quieter and louder through the melody; tell me if you think it goes too quiet.