USB Volume on Voicelive 3 Extreme


I'm using Onsong ipad App with my VL3X plugged into the USB port. When I play a track from the Onsong App, the iPad's volume up/down buttons don't work. Only way I can turn the music up/down is through the VL3X mixer (4 small knobs on face). This isn't very convenient as I have to bend down to twist the knobs. Is there any way to affect the volume with the iPad volume buttons or are they bypassed since I'm plugging into the VL3X via USB?