In reply to @sys64 "Variants vs inheritence, which": if youre extending some
type with extra features but still want to use it as the original type in some
circumstances you use inheritance. this is subtyping. if you want want a type to
contain different types and do something different depending on it you use
variant types. and if youre using recursive types youll want variant types. just
looking at your synthesizer thing I assume you want inheritance.
https://en.wikipedia.org/wiki/Subtyping
https://en.wikipedia.org/wiki/Tagged_union
https://en.wikipedia.org/wiki/Algebraic_data_type