I'm not sure if this is the right place to post this ... (there have been related threads under "technical issues" some time ago)
In my patch, I'm combining "sinesum" and "cosinesum" messages to calculate and then add the sine and cosine components of a waveform, using the Fourier transform idea. Furthermore, I'm not only calculating one single waveform but also a second one in quadrature to be able to do frequency shifting (this could, of course, also be done by simply using the Hilbert transform).
You can either draw the amplitudes and phases or calculate them. The chosen parameters for this may not be reasonable at all, but I really don't know how you would do this properly ...
I hope this is helpful for some of you.