Using references (ref) mixes of your favorite songs in the genre you are working in is a great way to calibrate your ears and compare your tones to ones you know and love. However…. It’s really common when mixing to reference tracks that have already been mastered to make the mixes VERY bright. Please pay close attention to the harshness aspect of these frequencies.
A mastering engineer does have tools to fix mixes that are too bright or harsh, but I’ve found over the years that starting with an un-hyped high end in the original mix allows for a smoother highs in the resultant masters.You may notice that after having a good mastering engineer work on your tracks, the high end feels very natural and bright without sounding harsh.
If you use refs, I recommend turning them down to be about the same volume as your mix, or a touch quieter, while you A/B compare. This offsets our ears’ bias in favor of low end at louder volumes.
You may find yourself boosting the high frequency EQ of your whole mix or the individual elements to match that of already mastered refs. Consider removing that kind of EQ, unless something is truly too dark.
This is an example of a pre-master mix file.
Typically, your mix will be much quieter than a mastered reference.
Be aware of how the volume difference can fool your ears in both high and low frequency balance, and be sure to turn down your refs to match your mix!