I have this idea to create a musical composition which consists of richly modulated overtones of a single note. (Hmmm ... wish I could describe that better ... )

I wrote a C program using libsndfile to do simple additive synthesis. I use a base frequency around 50 to 60 Hz and am adding harmonics from around the 7th to the 16th with different amplitude envelopes.

My plan is to create a melody with those harmonics, and calculate amplitude envelopes such that the note that is "played" reaches a defined peak amplitude at that time.

Here's the tricky part. When a note is not being "played", I still want the amplitude envelope for that harmonic to have a rich texture. I'd like it to stay below a certain threshold which I define, but it needs to be there, sinusoidally varying.

So, the question is, how do I get the Fourier composition of a curve defined by the location of various maxima and a threshold which the rest of the curve must not exceed? I guess I also need a parameter somehow controlling how quickly the curve must jump up above the threshold for a maximum and get back down.

My intuition tells me that if I get the formula right, the curve with the fewest sinusoidal components meeting my conditions will also have the richest variation in those regions of the curve which are beneath the threshold, and thus the richest sound texture.

Is this just senseless blathering to all of you? I wish I could make myself clearer.