Frets on Fire

Ultimately what I want to do is make some tracks for Frets on Fire given an MP3. I know I can’t do this properly, and that what I really need is access to the original, separate master tracks. That being said, I want to try my best to take an MP3 and from it generate a separate song.ogg, guitar.ogg, rhythm.ogg, and drum.ogg. These don’t have to be remotely perfect, but the purpose of the separate tracks is that if the guitar player misses a note, it stops playing that track for a moment so you can audibly hear the missed “note”.

What I’m doing currently, and is extremely imperfect is to use an equalizer effect to boost the 440Hz to 3500Hz range, and call this the guitar track. Then I take the original track, and lower the 440Hz to 3500Hz range, and call this the song track, that plays in the background. Next I take the original track and boost the 200-400Hz range for my bass/rhythm track. I lower the 200-440Hz levels on the guitar and song tracks. When I play all three tracks together, it sound like the original song.

Here is my problem currently. Initially boosting or lowering the 440Hz to 3500Hz range moves the vocals to the guitar track as well. I could attempt to use one of the plugins to remove vocals, and then boost the 440Hz to 3500Hz levels on what is left to create a better “guitar” track, but then how do I create the song track with the vocals restored, the the portions of the guitar track removed?

What I really need is a difference plugin that can compare two tracks and make a third. For instance, if I used a filter to remove vocals, and then used a theoretical difference plugin comparing that to the original track, then I’d now have a separate track with just vocals. I could also then separate the “guitar” range from the vocal-less track, and then recombine the guitar-less and vocal-less track back with the vocals to get my song.ogg file.

I also have no idea how I would attempt a drums track. I know that drums are all over the frequency range. Is there a way perhaps to just filter out the highest decibel portions?

Again, my final results won’t be anything resembling actually filtering out these individual instruments, which is impossible. I just want something acceptable that when a player misses a note, that they can hear audibly something is missing from the song.

I appreciate any help you can give me.

There are two effects designed for this kind of thing, but I’ve no idea how well they work. Before recent advances in digital analysis of audio made such things practical I would have said that you are probably already achieving the best that can be hoped for, but these effects may (or may not) offer a bit more:
Voice Trap
Extra Boy

Do let us know how you get on.