One thing that has interested me for a while is the different types of synthesis. It seems we can list the different types but that there is a fair amount of crossover between them. For example, is wavetable synthesis also subtractive synthesis seeing as it uses filters? And some FM algorithms are additive. Some forms of synthesis seem to have quintessential devices associated with them, like the DX7 or MiniMoog. But other forms, like granular or additive, maybe not.
It would interesting to have a conversation about how people categorize different types of synthesis and where the definitions break down or are inadequate for describing certain devices or software.