https://developer.apple.com/library/content/documentation/DeviceDrivers/Conceptual/WritingAudioDrivers/About/About.htmlthis seems to be about OSX.. but perhaps there is an earlier OS9 version that can be found. the article gives a hint at the old title "Writing Audio Device Drivers." so i will keep that in mind when im googling!
Who Should Read This Document?
As with any kernel-level device driver, you should only write a driver if there is no other way to achieve your goals. Many audio devices are supported natively in OS X. If your device complies with USB or FireWire audio standards, you should not need to write a custom driver unless you need to implement features beyond those supported in the relevant audio standards.
In some cases, even if you need to do special device-specific processing, you may be able to do so without writing an entire driver. For example, some USB audio hardware (for USB speakers, for example) may require additional software filtering, such as equalization. OS X provides a mechanism in the kernel for doing this through the AppleUSBAudio plug-in model. For more information, see the SampleUSBAudioPlugin example code
Topic: Introduction to Audio Device Driver Programming Guide (Read 3186 times)