How do i get my music from my iphone to my macbook air?

How did you get them onto the iPhone in the first place? Seriously, that pretty much tells you how you'll get them elsewhere...

Music that you've purchased from Apple's iTunes store can be redownloaded to other devices by going to the iTunes store and selecting the Purchased link. Music purchased from other sources or ripped from your own CDs will require a 3rd party application. I used to recommend Senuti when it was a free application. I'm not aware of any high quality free apps any longer (doesn't mean they don't exist, I just don't know of any). I got a program called PhoneView in a bundle and use it for those rare occasions I need to move music or other data from my iPhone that won't come out any other way.