Q: Apple Music account - move to a family plan - will i loose my music?

Hello Mark,

Thanks for using Apple Support Communities.

If I understand your post correctly, you would like to change your Apple Music plan from an Individual Membership to a Family Membership.  Check out the information below for more information:

Change from an Individual Membership to a Family Membership

With a Family Membership to Apple Music, families of up to six people can enjoy all of the benefits of Apple Music, each with their own library. If you joined Apple Music as an individual member, you can change to a Family Membership at any time. You can also switch back to an Individual Membership if you choose. You can also join an existing Family Membership.

To use a Family Membership to Apple Music, you must set up Family Sharing on your iOS device or Mac.

Manage your Apple Music membership on your iPhone, iPad, iPod touch, Mac, or PC

Cheers.