I have been looking all over for a program with the ability to search through my hundreds of MP3s and return to me the duplicate files: based on file size, ID3 tag, or file name. It would make my job cleaning my collection 100 times easier.
This is already on my wish list.
You should try Dupe Checker PRO 6.0. It's the best program of this kind! IMHO
Peace!
Try Mp3 Filter
I was looking for a duplicate mp3 finder too and found this old thread and the recommendations do not even exist anymore. I researched further just to find that most of those duplicate finders claim to find duplicate songs and all they do is find exact duplicates.
If you want something that works try this tool:
Duplicate Song Finder
It compares the actual audio in the files and can find similar songs even if they are not marked with ID3 tags. There is a mode to find similar ID3 tags too.
The internal preview is very cool to as it continues to play from the same position while you switch between the duplicates letting you hear which file has better quality.
You should mention that this tool is not free of charge:
(Current prices 12.02.2024)
and that these fees are one-time only:
and how limited the Standard-Version is. For example the Command-line features are only available in the expensive "Corporate" variant.
As this thread was started almost 20 years ago (and therefore some of the tools may not be available any more), I would like to lead the attention to more recent thread about the topic:
Oh thanks, I didn't see that thread. Still I don't see any alternative there. I've tried that Similarity app that is mentioned, but it does some spectrum analysis and lists very poor results.
Oh I see someone in that thread is as happy 
as me about this tool. Wish I saw it earlier. Tested 30 tools to find it.
I'm sorry, but neither me nor the op talked about price. I got the PRO version. $40 is a steal for the results it provides for the price of 5 cups of coffee at Starbucks.
What matters is -it finds similar songs that are not marked with ID3. It found even remixes of the same song. Nothing I tried was even close to what it can do - There's a free download if $30 is expensive for you. I don't need command line options, but yes that is steep.
P.S. If you are someone that doesn't pay for software you can use their free duplicate finder, but it finds only exact duplicates.
Btw, I avoid free tools lately as rarely there ones like mp3tag, and Notepad++ that are actively developed. I don't brag, but I donated to those too.
Just to add some more names of free tools:
Thunderbird mail client
Firefox browser
Foobar player
VLC player
Libreoffice suite
ffmpeg
mp3diags
Audacity
Gimp
As far as similarity goes:
I cannot share your opinion that it
as you can tweak and twiddle the thresholds. With those adapted to my conditions I found enough duplicates to find it a useful the tool. Or the other way round: I doubt that those few false duplicates and those few that were missed are worth the hefty fee.
But as we live in a capitalistic world, everyone has to find out for oneself if the price is worth the outcome.
I've only used it to find duplicate images so far but I was fairly impressed by the performance of this tongue-breaking open source duplicate finder. czkawka
Good list, off the top of my head I'd add Voidtools Everything, MusicBee, Advanced Renamer and PowerToys.