There was not an audience in the studio where it was performed. The audience for The Ed Sullivan Show was invited to stay in that theatre. They watched it on a large screen while it was being performed in a studio elsewhere in Manhattan, and it is their responses we hear. My guess is that the same basic thing was done with some other TV musicals, but Wonderful Town is the only time I've read specifically about it in an article from the time. But I'd think the same basic thing was done on, for example, the Martin-Raitt Annie Get Your Gun and the first Once Upon a Mattress, where we hear what sort of sounds like a live audience but something doesn't sound quite truly live about their responses, and the production seems like it must have required several soundstages (if that's the right term in these cases).
