Short answers, pulled from the story.
The earliest recorded instance of a simulcast occurred in 1926 when the BBC transmitted a Halle Orchestra concert from Manchester using the wavelengths of regional stations and Daventry. This experiment demonstrated that broadcasting the same content across different frequencies was technically feasible long before the word existed.
The term simulcast was coined in 1948 by a press agent at WCAU TV in Philadelphia. This definition emerged as NBC and CBS began broadcasting programs to both their nationwide radio audience and their growing television audience.
The band Grateful Dead and their concert Great Canadian Train Ride in 1970 was the first television broadcast of a live concert with FM simulcast. This event marked a pivotal moment in music history by effectively transmitting stereo sound to music broadcasts.
The first pop rock simulcast took place on the 27th of May 1974 when a recording of Van Morrison's London Rainbow Concert was broadcast simultaneously on BBC2 TV and Radio 2. This followed a live classical concert from the Royal Albert Hall on the 14th of November 1972 which was the first such transmission in the United Kingdom.
In greyhound and horse racing, a simulcast is a broadcast of a race which allows wagering at two or more sites. The process involves the transmission of wagering information to a central site so that all bettors may bet in the same betting pool while watching the race on a network such as TVG Network or the Racetrack Television Network.
The primary advantage of analog digital simulcasting is the elimination of interference and the ability to put 10 or more SDTV or two HDTV channels in the place of dropped analog channels. This method allows for smaller, cheaper cable boxes by eliminating the analog tuner and some analog circuitry.