Background Music includes code from Core Audio User-Space Driver
Examples, see
<https://developer.apple.com/library/mac/samplecode/AudioDriverExamples>,
which was provided with the following copyright notice and the license
below.
 
Copyright (C) 2013 Apple Inc. All Rights Reserved.

Background Music includes code from Core Audio Utility Classes, see
<https://developer.apple.com/library/content/samplecode/CoreAudioUtilityClasses>,
which was provided with the following copyright notice and the license
below.

Copyright (C) 2014 Apple Inc. All Rights Reserved.

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