Whilst looking for something else, which I found, I happened upon s series of circuits that were published in the UK magazine Electronics & Music Maker (E&MM) in the 80's. I do still have all of these magazines buried somewhere, but the online resource is excellent.
This link goes to the search page for the Circuit Maker articles. If it has a red dot then it hasn't been scanned yet. You never know, there may just be something there that tickles someone's fancy (e.g. the Real-Time FM Harmonic Generator). There are lots of other interesting articles on all manner of cicuits and synthesis techniques buried just in E&MM (e.g. this one on sequencers from 1983), and that's before you start on Sound on Sound and many others.
I was looking for the three-part series on The Psychology of Music from 1983. It seems slightly dated now, but there is still some food for thought in there
Actually, that graphic oscillator looks awfully tasty...granted, it outputs square waves, but there's a lot you can do with that when you start combining partials, plus the odd harmonic content will be interesting when the harmonics start to stack up.