Scott Morrison writes:

>Can anyone tell me what this phrase - 'ex aequo' - means when applied to a
>prizewinner in an international piano competition?

"Ex aequo" means "tied," that is to say that the prize in question is
shared equally by more than one person.

DPHorn, second prize "ex aequo" in the 1977 Kosciuszko Foundation Chopin
Competition.