To my ears, the magic is in the saturation, which adds a fizz when pushed to add presence and weight while also taking the edge off instruments, but not on all instruments so as not to overcook things. You cannot replicate with pure DSP/VST plugs even thought many try like UAD and WAVES as examples.

WHAT IS SATURATION IN MUSIC? Audio saturation is the essence of what makes analog hardware sound musical and pleasing. Driving sounds through tape, tubes, transistors, and circuits have long been an essential ingredient in great-sounding mixes. Saturation is a subtle form of distortion that adds pleasant-sounding harmonics. The effect originates from the analog days when audio recordings ran through various pieces of hardware. Mix engineers discovered they could overload magnetic tape machines, tube amps, and transistor-based preamps to create a type of “soft-clipping.” This technique gave recordings sought-after qualities that sounded pleasing. To this day, artists and engineers use saturation to add presence, character, warmth, edge, cohesion, and more. From subtle to extreme, saturation is an integral part of amazing mixes.

There it is.

Denser, Not Louder Because saturation works on the harmonics of a sound, you end up with something that’s harmonically denser rather than louder. There’s only so much room to go up in volume before you begin clipping but squashing something through a limiter or compressor is going to cause that sound to spread out instead. By taking up more of the frequency spectrum, you get a bigger sounding instrument. While that might sound great, the truth of the matter is that saturation needs to be used sparingly or its effect is negated in the context of a modern mix. Most mixes today are already super full of high track counts and lush instrumentation, so any time you add size with saturation, you’re eating up bandwidth that could have potentially been used by something else.