On the PA900 I can set an Assign Button to various things ... I have my 3 set at Mute Acc 1-5, Mic talk (which drops down the volume on the style, but not the mic) and Ritardando ... in the absence of 'auto mute accomp x when RH voice is the same instrument' how much more costly would it be to have enough assign buttons for each of the accomp parts ... right now, when I want to change in 'real time', I mute 1-5 and then go in and generally um-mute the guitar part, especially if it is just a guitar strum ...