So I looked into why there wasn't a USBAudio example and the basic reason seems to be that USBAudio doesn't work on the Giga R.
I looked into it a bit and managed to get it working, I have put in an issue here: USBAudio (Giga R1) Faulting - USBPhy_STM32.cpp connected to Mac · Issue #736 · arduino/ArduinoCore-mbed · GitHub
Maybe this can be passed on to whoever is in charge of this sort of thing at Arduino?
Cheers
Andy