Every example from the Learning Core Audio book rewritten with Swift 2.0.
The output can be silent when you use different devices for the input and output. As a workaround, try to change the size of the ring buffer.
The MIDIWifiSource crashes on iOS 9 + OS X 10.10. I was unable to test it with different OS's versions.
In case you're interesting in debugging it, the crash happens when the connection is initialized:
let connection = MIDINetworkConnection(host: host)