What is the most effective way to consolidate my iTunes library (there appears to be 2-3 separate origins)?

Hello all!,

I've come across a problem regarding the source of my Music files on my MacBook Pro, finding that my fairly large (76 GB) iTunes library is made up of files from a large range of locations. I've had this Macbook for ~3 years now & have never necessarily worried about the amount of audio on the harddrive. As I noted, I have 76GB of music on iTunes, but the "Audio" section of my harddrive is 215GB. Based on looking at the iTunes/iTunes Media section of my files I've come to the conclusion that my process of finding and adding music to my library has resulted in a large amount of duplicates and/or multiple locations.

I began by going through and deleting unwanted songs from my library, to see the effect it would have on the overall "Audio" on my harddrive. This didn't do much, leaving me with a ~54GB iTunes library, but a recorded 191.4GB of audio on my harddrive. It appears that the "Music" sub-folder of "iTunes Media" is a duplicated, older version of my iTunes library but I'm weary about deleting it in fear that the songs sources will end up "broken" and they won't play or sync.

I've browsed other questions and found scripts for similar situations but I'm not sure exactly how to go about using them, or if they're necessary/correct for this situation. What is the suggested manner for organization of music in iTunes? The suspected duplicates folder is located under "Music -> iTunes -> iTunes Media -> Music" and this seems like far too many folders for a library of relative simplicity.

The last question I have is if the albums I download are staying in my "Downloads" folder when adding them to iTunes, creating yet more duplicates (rather than simply being transfered to the iTunes folders)? I'd appreciate any help, hopefully I was clear about the problems I'm facing. The system I've been using works, but I want to get all of my audio files cleaned up properly.

Thanks!