Is there a free software to make my music files smaller?

My iPhone 4 is only 8GB and I don't have any other place to keep my music so I keep all of it on my phone. That takes up a ton of space and I was wondering if there was away to keep the song as it is but make it smaller

Type it in google or youtube

Making them smaller means you lose quality. Just offload some of them on to your PC, you don't need to have 4 gig of music on the iphone.

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