StepMania Helper Program

StepMania doesn't presently let you delete songs, but you can disable them.
I think that an integrated library manager would be a good addition. Just because the game doesn't have that feature now doesn't mean that it shouldn't.

I don't really want to delete songs from inside stepmania, because it's not easily reversible, and every OS (or desktop environment, on Linux) has a different incompatible way of handling trash/recycle bins, which would be a huge mess to support. It's less work for the devs and fewer accidents for players to just move the songs to somewhere else, or mark them and give the player a list, and leave it to the player to use the list to decide on permanent deletion or not.

Other library management stuff would be nice, though avoiding tripping over song reloading and caching problems would be really difficult.

Difficulty determination is sadly as simple as "number_of_notes / song_length". I'll agree that this isn't a perfect representation, but it does appear to be surprisingly accurate. Songs that could exploit such a metric, such as with a large amount of empty space and a small amount of extremely dense notes, seem to be fairly uncommon, perhaps because they aren't as fun to play. The standard deviation for each difficulty is then calculated, and depending on the filter intensity, any song not within a certain number of standard deviations from the mean are flagged. Even with the highest intensity filter, not many songs are usually flagged, although this does depend on how varied the user's song library is. The idea behind this filter was not to be nit-picky, but instead to catch songs where the creator was lazy and listed all difficulties as 1, or where they created their own difficulty scale that very obviously conflicts with that agreed upon by the community. I was tired of picking a song listed as being a 4, only to find out that it should be been labeled as a 15.

As for the 3 notes at once thing, I seem to have been called out on that by pretty much everyone. Although I've been playing for a decent amount of time, I would hardly consider myself a master at the game. On a good day I might be able to barely pass an official DDRX song rated at 14, but I usually don't play songs with a difficulty much higher than around 9. I play the game as an excuse to exercise, not to participate in tournaments or compete in leader-boards.

I'll investigate how feasible it would be for me to try adding library management to the game, but sadly my area of expertise in programming is simple firmware development, web programming, and windows forms applications; I have never worked on a game before, and cross platform development isn't something I'm used to doing. It might be a fun learning experience though.

Sorry to revive an old thread, but would it be possible for you to add a feature only listing the duplicates or dumping them into a log file?
The reason being if the file is moved outside of the folder, I have no idea which folder they belonged to in the first place.