Sound has a powerful and most direct effect on the human brain. Thanks to the Apple Core Audio subsystem, we can use this power in our Mac and iOS programs: capture sound from input devices, apply effects in real time, play MP3 files, play virtual musical instruments, listen to web radio, support VoIP technology, etc. The most advanced audio programming system ever created, Core Audio is by no means simple. In this edition, one of the best iOS programming authors Chris Adamson and legendary Core Audio specialist Kevin Avila talk in detail about this amazing subsystem so that programmers on Mac and iOS platforms can take advantage of all its capabilities. The publication is intended for programmers of various levels of training who create applications in Mac OS and iOS.