There are two ways for you to copy files from iPhone to computer.
One way: use wi-fi
Apple catches iOS up to the rest of the crew. If you have updated your iPad, iPod Touch, or iPhone to iOS 5 or iOS 6, your device will attempt to sync with iTunes anytime your device is plugged into power and connected through a wi-fi connection. Obviously, your computer will need to be powered on and iTunes will need to be running for this to occur, if have a large number of songs, this method is not suitable.
Wi-fi tutoail:
http://www.tech-recipes.com/rx/18351/ios-5-sync-to-itunes-over-wi-fi/
Two way: use Paid iPhone transfer app
iPhone to computer transfer app, of course, if it not exceed your budget, you can give it a try, it can move all files like music, photos, videos from iPhone to computer without iTunes library, there are also many free app but some function is not great, I won’t recommend.
If you’re PC users, you can follow this tutorial:
http://www.istonsoft.com/iphone/how-to-transfer-music-from-iphone-to-itunes.html
If you’re Mac user:
http://www.istonsoft.com/transfer-ipad/transfer-purchased-items-from-ipad-to-itunes.html
These two way can also solve your problem depend on the number of the songs you want to copy.