If you read the class/OOP part on the official lua page, you’ll find that a class is pretty much a template table with one of the elements being a constructor function. This constructor is used when creating copies/objects of this table/class. The constructor function and what setmetatable can do is pretty much what you need to understand to set up simple classes. But… one thing worth mentioning is that Renoise provides (via luabind?) an ‘enhanced’ way of dealing with classes that seems to be a bit more convenient.
Danoise has explained some of it to me in this thread recently: https://forum.renoise.com/t/creating-a-class-beginner-question/46235 It might help you get in the ballpark.
Thanks Joule! I’m still really confused about the metatables, so this will help.