It was not a very reliable method but it did work if you had good FM reception and a high quality tape deck. I guess it helps that the data rate is only 300 bits per second or so.
Haven't heard the audition, though. Well before my era.
Growing up in USSR I didn’t know anyone who would own a PC up until early 90s.
I know one programmer in his 50s. He had an access to the ZX Spectrum in his primary school, but that was by effort of his local physics teacher.
But I don’t get it then - why would they broadcast software for devices no one had?
That device had ridiculous capabilities. The sound chip was good enough people wrote a speech synthesis software. Later, people wrote a graphical OS, with e.g. a text editor being an equivalent of Windows Write from the 90s.