I began learning Swift by building something I wanted, a soundscape mixer that stayed out of the way on OS X and iOS. A few weeks ago I saw others were wanting the same thing based off the feedback in the Noisli thread, so now that the base features are done I wanted to share it. I'd love any feedback, and I hope it's useful to someone else:
https://github.com/lukeheuer/soundescape-osx
https://github.com/lukeheuer/soundescape-ios