Anonymous IP address for p2p

Concers over mass surveillance, hiding network identity and data retention are just a few reasons to use anonymous IP address for p2p. However there are many options:

Tor
Tor is intended for users that use anonymous ip address for other purposes than big p2p transfers so consider making at least a donation.

Proxy server 
Most proxy servers are not free and many p2p clients have trouble working over proxy server.

Connect to remote wireless network.
To connect to wireless networks few blocks away use signal booster. If you live near state border and can connect to wireless network in another state you can even trick geo-blocking..

labirinth of wireless networks

Share
Sharing devices bring some anonymity. Personal devices usage become "less personal" when whole family or company use same device (i.e computer).

Library/university computer can be used to make p2p transfer. Files can transfered to home computer with usb stick.

Remote desktop
Accessing home computer from office computer make some kind of "tunnel" that your boss will have hard time to "decrypt."

Is anonymity important?
Probably no, there are plenty of chances to listen to legal music and there are a lot of free software alternatives out there. Better way to achive internet freedom is to avoid webpages that requre registration.