Is theres a free app for music?

You cannot backup one iPhone to another iPhone. You can restore the backup of one iPhone to another iPhone assuming that both phones are yours and they use the same Apple ID on both.

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

You can get music from the iTunes app but you have to pay for the music.

you can backup a phone then you can restore that backup to a second phone.

what exactly is your question?