Try using two instances of Fresh Air. The first instance on an instrument bus (Drums) with Mid-High cranked. The second instance on the Master Bus with the High knob barely tickled. This cumulative effect creates depth. The individual elements have presence, and the overall mix has glue. The Verdict: Is It Worth It? To ask if Slate Digital Fresh Air is worth it is a trick question—it costs nothing. But regarding your time and CPU usage?
Digital EQs, by contrast, are linear. If you boost 15kHz by 6dB on a digital EQ, you get exactly 6dB of boost. If the vocal has a harsh spike at 10kHz, you just made it 6dB harsher. Fresh Air behaves like an analog circuit. It applies dynamic saturation.
Rebuttal: Linear phase EQs smear transients. Minimum phase EQs shift phase. Fresh Air uses a unique algorithm that reportedly avoids destructive phase cancellation in the critical 1kHz-5kHz range. In blind tests, most engineers prefer the phase coherence of Fresh Air over standard EQs.
It solves the problem of "digital coldness" instantly. It requires no manual reading. It is impossible to make a mix worse if you use the Mix knob responsibly. For years, engineers spent hours automating EQ shelves to avoid harshness. Fresh Air does that automation in real-time, for free.
Fresh Air does not have an internal sidechain. However, if you are using a DAW like Ableton Live or Reaper, you can create a parallel chain. Duplicate your track, apply Fresh Air 100% wet on the duplicate, and then EQ that duplicate. Cut everything below 1kHz on the duplicate. Now, Fresh Air is only adding air to the high end of your source, leaving the low end perfectly dry.