Hi Peter & Derek,
I don't know if it would work for everybody; I make my living as a composer, not as an artist performing on stage every night.
It makes sense to me to share as much music as I can with my fans and/or customers (music supervisors, music libraries, etc.).
The concept would especially work well in the long term since all the music done could be available to all the subscribers. As long as you keep writing, the fans will be happy to get more music.
...especially if you add some bonus materials.
I think it would work very well if you happen to make a story around each song.
Either you tell them a story about the lyrics, or something about the production process, the meeting with the singer, whatever is interesting and add value to the song.
Collaborating with graphic artists or filmmakers (at the indie level) would make it even better and worth something to the fans.
Basically, when you get your fans hooked by the subscription, you need to deliver as much as you can to keep them as a subscriber in the long term.
If you're good enough, you can even consider doing your booking for your shows through the subscription (ie asking your fans where they want to see you and wait until you get enough fans in one area before booking a show)
Other options could be to allow interviews from your fans in the private area. They become the interviewer and would feel special about this.
Those are just thoughts I have in my mind and that I'm willing to try in the next few weeks. I have no idea what the result will be; that's why it's interesting to get your feedback to see how this could be improved.