Android 5.0 (API level 21) and above supports a subset of USB audio class 1 (UAC1) features: https://source.android.com/devices/audio/usb.html
related links: https://source.android.com/accessories/custom.html http://developer.android.com/guide/topics/connectivity/usb/accessory.html https://developer.android.com/guide/topics/connectivity/usb/index.html
Can a USB audio class 1 device interface with an associated Android application via AOA?
It seems that Android can handle only one accessory at a time, so I can't present a USB audio and an AOA custom accessory on the bus separately.