Memory Help!

Hey everyone! I'm new here and new to the Mac world as I just got the Macbook Air 11' as my first Mac and laptop for my freshmen year in college. I love it so far! No really complaints yet but one thing I'm concerned about is the memory. I have a 121 GB Flash Storage and after about 2 months of having my computer it says I have only 12.78 GB free left of memory. That really concerns me because I don't know how my computer is already almost full. When I click the Apple Logo and go to storage on About This Mac it says that my largest amount of data I have is Audio which I have 69.49 GB on my Mac! I listen to a lot of music and all of it is on my iTunes, but when i go to iTunes it says i have over 6,000 songs which equals to 42.02 GB. Where is the other 27 GB from? I download a lot of music (free mixtapes, etc.) and buy albums off iTunes and I know that when you put a song in iTunes you automatically create a new folder under your Music folder through iTunes. For about a month I had double of most of my songs because half of the more recent songs I downloaded where still in my downloads folder and there were the actually files on iTunes in the Music folder. I've deleted all the music in my downloads folder but I still have 69.49 GB of audio yet only 42.02 GB on iTunes. Where is all this audio on my Mac?