I have to chime in about the running 2 channels,

when the Tyros 2 has left and right abouts used it will create stereo effects, also take advantages of the stereo samples, but if you sum left and right wouldn't that create phase cancellations, which in turn will hurt some of the sounds, yeah sure some sounds will be fine, but most that use some type of chorus or ambient stereo reverb will knock it self out.

do some research on phase cancellations and you'll see what I mean.,

I'm sure Yamaha thought someone would use it in mono and to set it up to work accordingly when plugged into left/mono out.

Also if you are using a mixing board and running that stereo your doing the same thing to that, in turn will probably create some of the hot feedback frequency's you are getting.

I have 4 of the Bose system which I use anywhere from 1 - 4 according to the players I'm with.

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