Q. Would it be correct to use an en dash instead of a hyphen in a compound like “singer-songwriter”? What about a slash?
A. En dashes may be used in compounds referring to two different people:
Epstein–Barr virus (a virus named for two people)
Ali–Frazier fight (a boxing match between two people)
a singer–songwriter duo (referring to two people)
but
Albers-Schönberg disease (a disease named for one person)
Though Chicago doesn’t require an en dash in those first three examples, some style guides do (notably in the sciences and in British English).
But when a compound refers to only one person or thing, as in the compound nouns singer-songwriter and city-state, most styles (including Chicago) would recommend using a hyphen.
As for a slash, that’s usually reserved for alternatives, where the slash means “or” rather than “and” (as in and/or but not singer/songwriter).