[Haskell-beginners] Haskore lib

Hi All. Is there someone using the library Haskore to handle music in Haskell? I'm reading some haskore manuals and now I'm a bit confused about the compositional operators (:+:) and (:=:). These operators are mentioned everywhere in the manuals, but browsing the library code and trying some examples I just found the operators (+:+) and (=:=). Which is the difference between (:+:) and (+:+) and between (:=:) and (=:=)? Thanks in advance. Luca.