You need to build your own Swift/Objective-C subclass of AUAudioUnit that includes your custom filter code. Once you have registered that with CoreAudio, you can create a node in your AudioGraph using your custom unit. Why can't things be easy? Found that source code helpful (but a little buggy): https://github.com/GeorgeMcMullen/AudioUnitV3Example/blob/0ab6f2feb953d37e4e7b2359627b97858b317bc8/Filter/Shared/FilterDemo.mm