They try and consolidate accounts. The partner is on the same as mine since they got consolidate yet have their own Google allocation and email address allocation. I don't think they are too bothered. Handy for those questions of "you did x or y was it you".
On deleting music if you have stored them yes if they are MP3 etc. I guess itunes is some account with stuff in it.
You'd pull them out and save elsewhere your "music", test, if it worked fine, put them back otherwise.
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Anybody who uses what they identity as 3rd party apps on your PC for email like old Outlook.... yes their new method works so they seem to have stopped hassling you about turning off third party app. They have another way that keeps themselves happy with a unique password they give you to put in the 3rd party app they didn't like. I don#t think it's cookie based but stops people hacking your email server... can only think they deemed Google accounts were at risk of that since 2nd Google email accounts were not, just the primary. Mutter that as an aside.