Just to see how Roland does their block diagrams, here is a scan from a
typical patch of theirs (Doepfer is very similar). Everything is in squares
but mixers and VCAs are triangles and voltage inverters are a triangle with
a bubble on the end (in other words, a digital inverter symbol). If you
want to stay standard and keep in line with what's already out there, this
would be the way to do block diagrams.
http://home.att.net/~elhardt6/Roland_Patchsheet.jpg-Elhardt