YouTube has clips of one of the most famous meetings of the theatre and television media: the 1953 Ford 50th Anniversary Show where Ethel Merman and Mary Martin -- the two most famous names on Broadway -- appeared together for the first time. The most famous part of the show was a 13-minute medley of Broadway standards by Merman and Martin.
The first ten minutes are here.
And the last three minutes are here.
A caveat is that by this time, Merman was past her peak as a singer. She compensated for this in a clever way: she started "scooping" on any note she didn't feel comfortable hitting directly (attacking the note from the flat side instead of hitting it dead-on), disguising her pitch problems and expanding what had always been a quirky trademark of hers -- she'd been doing the scoop for years, but mostly as a special effect; by now she was doing it all the time.
Still, this is a great reminder of that time in the '50s when New York theatre was at the centre of popular culture: with television mostly based in New York, audiences around the world could get familiar with New York theatre personalities and New York musicals; New York stars became international stars, and Merman and Martin in particular gained an international celebrity that they'd only fitfully had before (particularly Merman, because she didn't like to tour and therefore was rarely seen outside New York). The connection to TV is part of the reason why there were so many mega-hit Broadway musicals in this period. Eventually the centre of TV production would move to Los Angeles, and Broadway would start to decline in the wake of that particular shift.