Google Play Music is a pretty good service. You are able to buy and listen to just about any song you can think of. All the music is stored online so you don't have to worry about downloading songs to your phone taking up precious phone storage space. There are a few drawbacks to Google Play Music. You have to buy the songs you want to listen to from the GPM service. If you have music you already own on your PC or Phone you won't be able to upload it to GPM to store on the cloud, at least Google doesn't give you an option to do so. Also you aren't able to share songs between accounts which is a bummer since each family could have several different accounts.
There is a way to sync up your songs to Google Play Music. You will need a few things to get started. You need an "always on PC", Cloud storage service, Google Play Music Manager, An Android Device, and ES File Explorer. Once you have all of these head to the link below for the full guide.
via XDA