A colleague of mine (who catalogs musical scores) brought to my attention the behaviour of a word he sees a lot, versenymű. This full (extended?) form only seems to be used on its own, e.g. versenyművek orgonára és zenekarra. When the word is modified or acts as the second element in a compound, it is shortened to (remains?) verseny, e.g. Brandenburgi versenyek. This is true even when it introduces ambiguity, e.g. zongoraverseny is both "piano concerto" and "piano competition".
So what's going on here? First of all, do we have the usage correct or are there examples of versenymű being used in compounds? Second, is this common in contemporary Hungarian? I haven't studied the language much, but I can't think of any other alternations like this. (By contrast, they're all over Standard Mandarin, where there's a strong preference for bisyllabic words.)