Download iExplorer. Backup your phone and open up towards the Music section, and export all the music media to your computer. When syncing with iTunes, if it asks for you wipe your device and such before syncing, make sure you've logged into your AppleID that's linked to your device before syncing. If you do this, it won't erase the data on your device. But before doing so, it's best to use the iExplorer method first before attempting to sync
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