TL:DW; Monitor through these plugs to hear only the highs, or only the subsonics, and adjust your mix accordingly. Also works as special effects.
By request, here’s my mix monitoring tools, for VST and Audio Unit, Mac and PC! Please remember, these like Guitar Conditioner are control-less plugins so you don’t operate them by opening their windows: they’re either on or off, which probably is shown in your DAW mixer window already.
SlewOnly gives you what it says on the tin: only the difference between samples, expressed as a sample. This produces a super-bright sound with zero latency and absolutely no pre-ring or post-ring. You can do two poles of this filtering: just add another SlewOnly. But, as is, this will give you an incredibly clear and transparent window on the ultra-highs, so you can dial in subtleties in the treble. Beware: don’t switch right back to the normal sound or it’ll sound incredibly dull. Rest your ears for a moment before resuming work.
SubsOnly does the same thing for subsonic bass. It sounds a little like a house party from an adjacent house. You can tweak sub-bass elements and really hear how they’re balancing against each other, and if you’re packing too much into the subs you’ll hear that as well. Get things thumping properly through SubsOnly and it should translate well to all manner of bassbins and subwoofers.
Lastly, these are calibrated (in SlewOnly quite literally: pink noise will be about the same amplitude with or without it, though the tone will be way different) so that you can switch them in and out, and expect roughly the same loudnesses. It’s okay if SubsOnly is louder for fullbodied bass: with that, it’s not so much about level-matching, it’s about getting your sound (at whatever desired loudness) and then having the bass still make sense through SubsOnly. If you’re madly overloading it, there won’t be groove, just a lot of thunder and noise, at elevated levels. These go on at the end of your master buss, so you can hear what your 2-buss chain did to the sound. Especially if you try and go for ‘commercially loud’ volumes, sanity checking with these tools can be a real silver bullet.
Like my other VST plugins, SlewOnly and SubsOnly are supported entirely by a Patreon. This is going to grow until it replaces the income I used to make by selling my plugins for money. I can’t justify charging musicians (many of whom aren’t earning money themselves) $50 a pop just to use my tools, so I’m in the process of porting everything I’ve ever made, to Mac/PC VST, and making it all free (even open source). Supporting the Patreon furthers that goal.