It is often thought that in order to get a good recording everything has to be isolated.
“There can be no spill between instruments as this will make mixing extremely difficult”.
I’m not sure where this train of thought originated, but I can guess it only became an issue with the rise of multi-track recordings and the need to keep things clean on their respective channels and to allow the ‘perfect mix’ to be created.
Sometimes though you actually want a bit of spill and other times…. you wont notice it anyway.
The ‘dreaded spill’ really only becomes …