I'm hoping to identify a shareware utility that I first came across several years (maybe 5-10) ago when it was the subject of a package on BBC Radio4's Today programme.
Basically, it was capable of processing an MP3 file of a music track, say, and decomposing the sounds of the various instruments into a "score" which could then be used, via its GUI, to produce a remix of the track, e.g. emphasizing one instrument over others. It worked with mono and stereo sources, and did not require access to an original multi-tracked recording. To do that, I assume it must have done some frequency-domain and time-domain analysis of the signal, because it was capable of distinguishing and separating out the sounds of instruments which would occupy similar parts of the audio spectrum, e.g. a guitar, piano and wind instrument. Analysing the file was certainly very processor-intensive, as I recall.
ISTR that the author was British and the utility was shareware; I had a registered copy of it on my then-current laptop, but it never made it onto the laptop's replacements.
Can anyone identify the utility from this description, or suggest a functional equivalent?