A Good Phone Manager, it allows you to add songs to iPhone without iTunes and help you to manage iOS devices easily and effortlessly.
iTunes is one of the best tools to transfer music from your computer or Mac to you iPhone and manage the songs well. However, it requires you to pair your computer with your iPhone, which means you have to sync your iPhone with the paired computer. Otherwise, you'll lose songs on your iPhone.
iPhone Transfer can add music to your iPhone without iTunes easily
here is a transfer music to iphone without itunes guide
Transfer iPhone Songs to Mac without iTunesPart 2.
Transfer iPhone Songs to PC without iTunes