Its been a while since I was here but there were many clever people about the place so hopefully someone who's interested in the topic would like to make some suggestions. I also figured the Analog forum (here) would be the most educated/enthusiastic on the topic...

I'm doing a bit of research into musical signal distortion of the broad kind (any change from input to output), but am particularly interested in the subtle distortions such as saturation that are more to do with perception than clipping. I was wondering if any body around here could recommend some AES papers or good books on the subject (preferably papers since I have unrestricted access but if theirs a book I 'must read' I'll look into it).

Obviously I've done a search of their site turning up loads of information (some relevant some not) and I'm looking to filter out the noise and find the most related.
A good example I've already found is Russell O'Hamms paper on Tubes vs. Transistors where he relates the extra presence of even harmonics in valves to musical examples like a closed trumpet.

In a nutshell I want to research why we perceive certain types of distortion as musical (e.g. tape saturation) and why we perceive others as unmusical (digital clipping).

I don't want to limit myself to the typical thought of distortion (buzzing sounds) because as far as I'm concerned ANY change to the signal is distortion.
Good papers/books on the musical design of analog/digital filters for instance would also be of interest.

So, have any suggestions?
Thanks in advance

p.s this place has really been updated since audio fanzine took over...