I am reliably informed that 'harmonic' distortion is anything that 'distorts' the audio signal by adding in extra harmonic information - new frequencies. This CAN be musical - as in the case of valve technology, where people buy a unit especially FOR the harmonic distortion - or it can be a pain in the arse - like my Gemini mixer with a relatively high level of harmonic distortion, which makes everything sound dirty and less separated.
People pay large amounts of money (like, around a grand for a DJ mixer) to remove this distortion so they can hear all the separate layers in the music clearly - or in the case of producers, put them there cleanly in the first place! I found things much easier to produce when I removed my DJ mixer from my production system. When I then went back to Reason, everything sounded cloudy again.
Think of it this way - if each layer in Reason has a little harmonic distortion and they all stack up, you'll get loads. You don't use a valve unit on every layer in your track separately, do you?
I doubt individual layers in Reason display much in the way of quantization noise - according to the manual, the signal is kept as a floating-point representation throughout the system, until it hits the audio interface. (This is why you can't get the system to clip until that point!) It doesn't sound like quantization noise, either... That's pretty harsh stuff.
I'm saying that, yes, different sounds interact with eachother to create new information as phasing effects create new frequencies and calcel out others... But Reason seems to add *more* mudge to this process than Logic or Cubase.
;)
Try listening to a burned-off wave compared to Reason playing live - I seem to remember things sound sweeter when burned off. Especially if you're pushing the processor when you're making the track. It could be some optimization routine...
Finally, try using a vitalizer - either a plug-in, or get one second-hand. They're cheap now, and (so I'm told) attempt to remove 'wasted' frequencies. Sounds strange to me, but there you go! I've only heard good things about them.
Tequila