Mozart and Bach both lived before copyright.
As a matter of fact, there's an amusing story about Mozart as a child. I think I remember the gist of it. He attended a performance to which it was forbidden to bring paper and pencil, and afterwards asked the purpose of the restriction. He was told it was to prevent the audience from transcribing the performance and then selling it. Mozart then played the entire piece from memory.
So I guess claiming Mozart for the RIAA's camp is questionable.