I'm sorry but I think this is a failure of strategy.
Musicians use social networks to reach existing fans and acquire new ones. Speaking as a musician, ten years ago we were all about Myspace. These days we're on SoundCloud, Facebook, YouTube, and Twitter. We don't use Myspace because nobody else does either. We use YouTube, FB, and Twitter because everybody else does, and we use SoundCloud to share new music with hardcore fans and with each other.
If you're looking to share your music with as many people as possible, you put it on YouTube, not SoundCloud. If you want people to go to a show, you talk about it on Facebook or Twitter, not SoundCloud. If you want to get a label to sign your new track, or you want your hardcore fans to be able to hear your newest music right away, that's when you go to SoundCloud. If you're on SoundCloud, you're either a musician, a hardcore fan, or, more often than not, both.
What I'm basically saying here is that a social network for musicians gets something very fundamental backwards, because of the four social networks musicians use, SoundCloud is the least important, the least promoted, and also the only one which was actually built for us.
I'm not trying to denigrate SoundCloud, it is in fact awesome and incredibly useful, but it's so much more important for a musician to be where the fans are. Also, if your goal is to occupy a smaller niche like SoundCloud does, you're still more likely to succeed building tools which make it easier for a musician to graduate their fans from the "hitting Like on YouTube" level to the "downloading everything on SoundCloud" level.
I think this is kind of like, "I want to make a social network, what's a topic, musicians, ok go." Rock on, it's good to stay focused and keep shipping, but it's better to make stuff people want, and believe me, what musicians want is to be able to make music as much and as often as possible, and that means making money from music, and that means either fans or students.