But you don't need to do anything to join, in fact there's nothing to join! I don't like going to live concerts as I find them distracting. All you need is a CD and preferably a pair of headphones and then you can be a member of a one-person club. Just you and the music.
I really don't care at all if people like musicals over other things. As you say, it can be a step in the right direction at least. I was just a bit disappointed that after all the televised Prom concerts we've had, plus the ones on the radio, it was the R&H one that has received the most feedback. It's no surprise really as obviously it's popular, but I personally believe that, as music, there have been much greater things on offer. No-one but me even commented on the Symphonie Fantastique, one of the greatest, and most influential, products of 19th century Romanticism and which was shown on TV a week or so ago.