Q: Changing my ITunes account on Apple TV how?

As far as I know the email used as an AppleID for itunes cannot be changed though you can change the correspondence email and account password which is what I assume you want to do assuming you are the purchaser of the music etc.

Manage the ID here:

https://appleid.apple.com/cgi-bin/WebObjects/MyAppleId.woa/

I still have an old defunct email address as my AppleID for iTunes - just regard it as a unique iTunes username - the fact it is an email address is not relevant.

AC