Colors for Ears

I forgot my headphones today, so had to borrow a set from a friend. Normally headphones are like bridges, they faithfully pass on (or don't) what they receive. This one had NAT; it looked at what it received, 'decided' where it needed to go, modified accordingly and then passed it on. I am not well versed in the language of bass and treble to explain what exactly it was doing, but it was crazy. For some songs, barely audible notes that I had never noticed were playing full steam. For others, solos had turned into chorus. Tones had shifted and words had vanished, all over the place. It was like looking at the world through colored glasses.