This may or may not be of interest to you as it was to me.
I have always used the Kn7000 for playing all sounds from the computer. The Sound goes from the Media Player down the USB cable into the KN7000 and it plays the midi or wav or whatever but not movies
You need to know that the Yamaha Tyros 2 board cannot be used this way.
I just had a pleasant phone call with Steve Deming at Yamaha Support (courtesy of Dan O'neil) and he advised me that I was trying to do the impossible. So I am back to the drawing board. I shall just run the computer feed into the Mixer and out to the sound system.
Best to all
Bebop
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BEBOP