anyone who knows about recording

is there a way that you can undo a mixdown of a song?

mixup

mixroundandround

No, the only way you could get the mix-down of a song was if you recorded the track (with Pro-Tools or something similar) and kept all the individual sound files etc.

If you're asking if you can rip an MP3 and then undo the mix down or something, then no, can't be done.

It's like trying to extract individual brush strokes from a painting.

Once the signals are summed and recorded mixed together, there is next to nothing you can do.

If you want a particular part of a song (most popularly, vocals) the best you can do is use some type of FFT noise cancellation algorithm, but this only works if you have a recording of the part with the vocal (or whatever you want) and a very similar part without the vocal, for instance.

Hope this helps.