Air is a term used to describe that high and lofty feel to a mix. Sometimes your mix may get muddy or you just want to get a bit more high frequency into it. “Air it out” so to speak.
The U-he Satin plugin is based on tape and there is an old trick that studios did to air out a mix using tape. It was to record at a high speed and playback at a lower one. I’ve made a preset for it and you can download it. Here is what I did to replicate it and how I use it.
I upped the tape speed on the recording head (Rec EQ circuit) to 15 i.p.s. and then repro’d it at 7.5 i.p.s.
I put this instance of Satin on the synths bus and it really airs it out. You could probably put it on a single instrument or elsewhere in the mix like on the drums, but I haven’t tried that.
I use a different instance of Satin on the master bus to give HX Pro type of tape effect. There is another preset for HX Pro type of tape effect described here [click].
U-he Satin is an excellent plugin for simulating tape and you can find it on the U-he website.
Lars Lentz Audio™ 
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