After toying with Audacity for a while and figuring out this awesome feature called “noise removal”, which has been quite helpful once I discovered it, I decided to try the effect out for music. However, it turned out it does not work that great for music, which is sad, but understandable, because of the complexity of the audio track.
Then, I started to wonder, if it is possible to separate loops from audio tracks. Obviously, if a track contains lots of other sounds on top of the loop, removing a loop from a song does not work that well, if at all, but imagine an audio track that has a mere loop at the beginning and then the loop plays almost throughout the whole song with some additional instruments. Here is the track, from which I’d like to remove the loop from: http://www.youtube.com/watch?v=lksNIHjYjSY
And yes, I know, the game is quite bad, but the music is pretty cool.
If the filters were perfect, then, sure, we could take anything out of anything. But they’re not. There are techniques to remove and separate all kinds of things, but nobody would mistake the result as a desirable music performance. One problem is the main performance hitting the same notes by accident that the loop has. They both go leaving holes in the show.
The reason music doesn’t work so well has nothing to do with the complexity of the waveforms or data. One of the Noise Removal tricks to keep voices from turning into trash is stop removing noise during vocals. Audacity thinks a continuous musical performance is one voice and stops removal. You can reduce Smoothing to zero and see what it’s going to sound like then. It’s usually not very pretty.
If I have some red paint and some blue paint in a bucket, and I stir the bucket clockwise, then I will end up with a bucket of purple paint. So if I then stir the purple paint anti-clockwise, the purple pain will separate out into red paint and blue paint Umm… no that does not actually work. Once the red paint and blue paint are mixed together they stay mixed together and no amount of “reverse stirring” will separate them.
Very nice analogy Steve.
Nevertheless, programmers and scientists are still trying to separate the two colours - even if they have to pick them pigment by pigment (a little easier if one would be magnetic…).
If the loop were really constant throughout or we had the original loop, your demand could be fulfilled - by spectral substraction.
The next best is to remove the center (with drum and bass mostly) and keep the right channel, where the melody dwells.
You can try it yourself by downloading this plug-in: https://forum.audacityteam.org/t/karaoke-rotation-panning-more/30112/1
(Place it in the Audacity Plug-in folder and restart Audacity - it will be found in the effect menu “2D Stereo Toolkit”)
Simply choose “Remove Center”.
You can then split to mono (track drop-down menu) and remove the left (upper) track.
More isn’t possible - as far as I know.