This may be a well-known bit of notation, but I've not come across it before. A friend is starting out on classical guitar (having strummed folk tunes for years). On one of the pieces she has - plaisir d'amour - is written in classical style with chords implied by the individual notes. Over some of them, though it says 1/2CH. What precisely does this mean? None of my music notation books says anything about such a thing.

If it is something that everyone knows, apologies, but it did not show up in Google search or a search here.