The title pretty much speaks for itself. I know that we've had only one musical number so far, but I still think that it pretty much gave us all a good sample of each and every one of the characters' singing voices. If you want my opinion, here's how I rank the entire cast's singing voices:
Bold = To me, their singing voices sounded just like their regular voices.
Italics = My opinion could change, since they either only talked, sang with groups, or just haven't sung yet.