STM32 Audio class USB not recognized as audio device
Have you tried this function?

USBD_Init(USBD_HandleTypeDef *pdev, USBD_DescriptorsTypeDef *pdesc, uint8_t id)


The documentation for this library is located here, but it's not great. In general, the HAL gives you some functions and if you use them correctly, a lot of other things happen behind the scenes. Your USBD_AUDIO_Init may be one of those things.