Another audio technical secret that I think it’s worth talking about is mid-range. Those who control this spectrum will create a good sound.
This is a very good article from the Line 6 knowledge base talking about mid-range and why someone who ha put together good sounding guitar simulations back home might encounter that in a loud scenario those pre-programmed sounds no longer sound good.
To be brief, we humans based on evolutionary needs could hear more details in the 2kHz range. This is where the human voice is operating. The old loudness trick with Hi-Fi equipment in the seventies was to make a happy curve, emphasize the low and high end and cut out the mid-range, resulting in more details heard outside the 2kHz range, so that it sounded more full.
However, when you boost the volume the ear no longer follows this model, so suddenly you get a sensation of loud highs and wooden mid-range. This is why many guitar amps such as Line 6 sounds good in a bedroom environment — you can’t shred with 120dB volume, but when you take them up on stage they sound tiny and shill unless you have a different EQ provided for stage use.
Mid-range plays an important part in many cases. In the case of bass playing, I’ve seen bass amp setups where the low end is maxed to 11 as well as the treble but the mid-range is decreased. So the bass sound has this low air-moving property but no sound or melody. I usually just go in and do the opposite, take down high and low, and instead play with the mid-range settings to increase that level. If you key in a good sound using mid-range controls, you both get a strong bass signal and the audience could even hear the bass lines. Amplifiers such as MarkBass have taken this to a scientific level — I still think the reason MarkBass sounds so nice is that they have a strong audio signal coming out on the mid-range levels.
Discussing about mastering, again I feel that any plug-ins that could enforce the mid-range dynamics without causing a wooden sound are great. You could achieve this with band-pass compressors. In my case I use VintageWarmer, with this plug-in I could increase the mid-range dynamics without it sounding too messy.
Anyway, I recommend experimenting with mid-range, if you control this area, in other words avoid the dullness but provide dynamics, your mixes and sound will be taken to a totally new level.