This is straying from the way things work on the SID, but given that Chipsounds is mainly a tool for making new music, and not one for playing existing music, I don't think it matters a great deal, and if we really wanted the frequency to be tracking other audible notes, it could be done with midi CC's and a bit of creativity.
That's my take on the matter, anyway, I don't know what other people think.
[Edit - another alternative would be to take the frequencies from another midi channel, perhaps?]
As a side note, I read somewhere that C64 ringmodulation isn't actually a multiplication of two waveforms, but rather some weird waveshaping or something. Information is pretty vague on the subject and there's a lot of misinfo. out there, but whatever it is, it's a freaking cool effect
