Musicians frequently get taught music in large batches at schools, though, which means you don't have to worry about network effects—there are choke-points in the network.

There's no reason a given school couldn't teach a "colloquial notation" first, with the "Lingua Franca" musical notation taught later on, for everyone in that given school. Then everyone who comes from that school would know that colloquial notation.

Consider: the "Chicago school" of Economics; "Rugby School" football; etc. These things start as colloquialisms, then spread to global awareness.