How to remove your Google Music account

From the Android Market FAQ on https://www.google.com/support/androidmarket/bin/answer.py?hl=en&answer=1186964&topic=1100184:

To delete your entire library and withdraw from Google Music, visit https://music.google.com and select ‘Settings’ > ‘Withdraw from Google Music’.

Direct removal link: https://music.google.com

Helpful Trick: Removing online data

Publicly visible text/images often aren’t properly removed even when you succeed in removing an account. Try editing or removing them manually before removing the account itself. If you’re unsure what happens to your tracks: this can be found mostly in the Terms of Service/Privacy Policy; otherwise you can always contact Google Music and ask personally. By the way, removal requests don’t necessarily mean your data will actually be removed (e.g. due to legal obligations).

Helpful Trick: Remove third-party logins

If you signed up for Google Music using a third-party login such as Facebook or Twitter, you probably want to revoke all access from Google Music. Click here to find out how.