Similarity finds duplicate music files using file names, metadata tags, and a proprietary audio analysis AND makes it easy to remove them. Really simple. Works great.
I usually start with the highest matching choices (100% or close to) and this takes care of the majority of files with no sweat. Then I dial it down a bit and start weeding those out too. I can get by on the free version (I have about 24K audio files) but the pay for version has more bells and whistles if you want. Works on most all types of music files (MP3, AAC Apple audio files, M4A, WMA, OGG, WAV, lossless FLAC, APE, WV, MPC, etc.). Fantastic job on this utility.
Lifehacker likes them too