I want to download music from Iphone 4 to my computer

I had to re-install my OS on my computer. I had my music backed up. After getting my PC working, I installed ITunes and added my backup folder to the library. I seems I have music on my phone that is not in my ITunes nor on my PC.

I would to download the music from my IPhone 4 to ITunes or better to a folder on my PC.