Ask HN: I've never done a launch before, can you guys help me out?

I suspect that my situation is sort of unusual so I'll try to explain it first as best as possible. I've decided that generative art/music is an interesting market, and so I originally was going to make synthesizer apps for Android. After much thought, I decided that a musician centric app, (not to mention a professionally useless one) excluded too many people. So my compromise was to make a series of sound organisms, each with a distinct sound, behavior, and visual style. Similar to RJDJ(1) or Brian Eno's generative sound apps(2). I figured this would be a good idea because IMO the aforementioned apps are a bit too hard to grasp for the average user. People might sympathize more with a creature that produces sound as a byproduct than a generative sound application with abstract visuals. At least that was my reasoning.

So the actual project is going along nicely, but from reading HN a lot I realize that the launch and marketing are pretty important as well. I don't know anything about marketing or launching a product. I was planning on charging $.99 for each app (each creature would be an individual app), and for my website I would have a splash page with a video, some QR codes and links to the apps in the market. Besides posting to HN and Reddit, what else can I do to spread the word about my apps? Should I set up the splash page now and gather emails? I don't know if people would be that excited about something that is kind of hard to explain without watching a video, which is why I'm hesitant about trying to build excitement without a finished product. Any advice would be appreciated, thanks.

tl;dr How do you market an app?

http://rjdj.me/

http://www.generativemusic.com/