Music on iphone not appearing on itunes?

I have alot of songs on my iphone, but only some of them appear in my itunes library on my computer? There's alot of songs that appear on my iphone but arent appearing on my itunes library, why is this and how can i fix it?

Perhaps when you first set up your iphone, you set it up so that iTunes and your phone would sync (share apps, music, videos) only when you connected your iphone to the computer, instead of Wi-Fi. Just connect you phone to the computer through the USB cable, turn on and connect to iTunes. And sync your phone to it. Your account should get all the music from you iphone and put it on the computer.

A device's backup doesn't contain the contents of the Music nor Videos apps. If the songs are still on your phone then you should be able to copy them over to your computer's iTunes via File > Devices > Transfer Purchases
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