[nightchef]

I think the right word for playing a piece written for one instrument on a different instrument would be "adapt" or "arrange".

To the OP's question -- all the time. I've been in cover bands where I was the primary vocal arranger, and I've had to break down complex harmony arrangements from groups like the Mamas & the Papas or Temptations, and it can drive you crazy trying to pick out that one squirrelly note in a complex mix, especially on old records with dense mixes where it's hard to draw the line between an overtone of Track A and the fundamental of Track B because it's all kind of washing together.

Sometimes it helps to bring the recording into a DAW and do some radical high- and low-pass filtering on it -- isolate the part of the audio spectrum where the thing you're looking for is. Sometimes that doesn't work and eventually you just have to make your best guess and move on.