Ric F wrote:
It's not really Apple at fault. There are plenty of audio interfaces that work just fine with El Capitan because the manufacturers use the native OS functions to connect their devices. Avid (and some others) wrote their own bespoke audio interface drivers, and it is this software that is incompatible with El Capitan.
This statement is (mostly) incorrect, it is companies who write their own drivers, (MOTU and RME), that have the most efficient, best performing audio interfaces. Apple's system drivers either change or are modified with every Operating System upgrade, including incremental upgrades so you never know what you're getting. Many of the USB devices that have failed do use Apple's system drivers. (personal opinion) Because USB uses the computers CPU to manage data transfer it is never the most stable audio interface. System drivers are constantly being changed to follow new standards, every upgrade is a crapshoot.
Generally speaking, professionals who rely on performance and stability seldom upgrade a perfectly running system, many here still use Logic 9.8.1 on hardware running Snow Leopard. What's more important, stability and performance or running the supposed latest and greatest (inefficient) OS?