Thanks for the file.
I had a smaller version of this piece of music, not sure if it's just part of the whole piece, and I've now found an even larger file which may be similar, or maybe a bit more jazz? Your file is 71,634 filesize, the jazz one is 99,511, so it's maybe 30% larger?
The files seem to comprise 2 tracks ONLY, and all the notes seem to be on one channel ONLY (Channel 1).
I've converted your file to .TXT, and been looking at that. It should be quite possible to do something. The main problem seems to be that the notes On and Off are not too tidy! Just on the first page or two of the data, I could see places where some notes ON were followed by the associated Note OFF, incl places where there was a clear chord ON and then the OFFs, but there were visible instances of, say, 3 notes on, then 2 notes off, then other notes on, and other notes off, and then the 3rd note from the first group finally off. makes things more difficult to keep track of.
Once the file is in the text format, then it would be possible to write a BASIC prog to step through the file line-by-line, amending lines as it goes. Because of the overlaps, it might be better to make the prog simpler, i.e. make certain changes in the pass through, but then make later passes through to make other changes, until there are no more 'track' chords.
As the piece is piano solo, there should be no more than 10 notes at a time?
Anyway, I'm talking of doing it 'manually', yes, but with massive computer assistance.
I may try and do something with the first couple of minutes of the file, so you can try it and see if it does the job??
OK?
Geoff