Problem with channels mx49

I have the mx 49 yamaha and it comes with cubase. Anyway, when I want to use the voices i can only play two channels or two voices without others voices.
I mean, I set the first two channels and everything is okay and they play by itselfs but on the 3rd the voice comes with the other voice that its set by the mx49.

My request is if I can mute the voice on the mx or if i can filter the sound and only play the voice on the channel that I want.

I dont have problem with record; when I do that, every channel is set with the voice that i put on the voicelist. This problem appears when im jammin or playing around.

Sorry for my english and thanks :blush: