no more audio through the usb to thx

when playing a backtrack it would push the audio through the usb and into my Yamaha thx 10 it must be somthing changed in the software becxause it still pushes all other sounds from the laptop into the yamaha but not the back track just comes out the laptop speakers please help win7 ver 2.12 into Yamaha thx 10 thanks for any help at all

Where is the backing track? Is THX10 a guitar amplifier? How is THX10 connected to the computer?

To play a backing track in Audacity while recording, click Transport > Overdub in the Audacity menus.