Modal concord refers to the phenomenon where the co-occurrence of two modal elements with the same flavor and force (e.g. may possibly, must certainly) gives rise to the interpretation of single modality. Given their (arguably) equivalent semantics, constructions with modal concord and single modal (e.g. may, must) can function as alternative choices in different contexts of use – how do speakers choose between them, and how is the choice perceived? In this article, we take a ‘Register’ approach and report an experimental study of MC in US English, addressing their linguistic and social meanings with versus without situational context. The results show that (i) modal concord constructions differ from single modal ones in linguistic meanings, which casts doubt on the concord assumption, and (ii) modal concord has distinct social meanings from those of single modal constructions. Our findings suggest a correlation between the meaning strength of a linguistic expression and the social perception about the speaker. Context, manipulated via the single situational parameter of interlocutor relation (close vs. distant), did not interact with the linguistic or social meaning of modal concord constructions, the implications of which are discussed in relation to the multidimensional nature of conversational situations and the method applied.