Hmmmm.. You may have just answered the question.. Turning the accomp volume down all the way would also do the trick on my PSR-550.. Have you used the drum machine in record mode? Were you able to record songs and have the RX5 sync up properly?
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GEAR: Yamaha MOXF-6, Casio MZX-500, Roland Juno-Di, M-Audio Venom, Roland RS-70, Yamaha PSR S700, M-Audio Axiom Pro-61 (Midi Controller). SOFTWARE: Mixcraft-7, PowerTracks Pro Audio 2013, Beat Thang Virtual, Dimension Le.