I started with the Qt multimedia audiooutput example. It produces a sine wave tone on my PC and it works fine on my N8. I added a new QThread to the program. It still produces sound on my PC, but stopped producing sound on my N8. I spent a week trying different ways to make it work on the N8 but no luck. I believe the QAudioOutput object creates its own QThread, and the QIODevice object also creates its own QThread. So there may be a limit on the number of QThreads allowed. Or could it be that the API library accessed by the Simulator release version, which is not packaged with the library for testing purposes, has limitations?