By "mathematically neat" I mean what you said; periodic function composition which is a nice general model in the mathematical sense but not specific to audio s

By "mathematically neat" I mean what you said; periodic function composition which is a nice general model in the mathematical sense but not specific to audio synthesis like the "ADSR" model is. So we may be singing from the same hymnbook here. What I meant by advanced digital techniques is I suppose anything that takes things into the frequency domain, manipulates and converts back. Physical Modelling, Impulse Responses and Digital FM are all fine things but not in this category. I used to have a plugin that did weird things like let you stretch or clip the frequency domain for example. i.e. a 1-2khz bandlimited signal would become a 0.5-4khz signal. Some of the effects in Razor also do things in frequency domain that you wouldn't really do in the standard subtractive model. My personal perception of Razor is that if you don't use those effects then it just sounds like a subtractive synth (same as before), while if you do use them it sounds a bit lo-fi (undesirable in my book though I appreciate that can be an artistic choice). Digital FM on the other hand sounds very clean to me.