This page from Margarita Escobars' senior thesis for the University of Miami on PsychoAcoustics
Does anyone have suggested reading material for mixing guitar and
contains a lot of conceptual information for anyone who is learning about mixing.
The whole page is a fascinating read but pay special attention to sections
2.7 and 2.8 on Timbral 'Masking' and 'Critical Bands'
Because guitars and analogue synthesizers are frequently in the same frequency bands,
these two concepts are absolutely crucial for mixing.