Sorry for my lack of technical knowledge, but we all have to start somewhere. I have, until now, recorded music using a pair of omnidirectional or cardioid microphones. I am considering purchase of a mix-pre-3 machine and intend to use it primarily in the same way. Unlike my current recorder this accepts, as indicated by its name, up to three microphone inputs. I understand that if three microphones are attached, the recorder will display the level of sound being from each plus the overall level of sound in the right and left channels. How does the machine know which of the XLR inputs you wish to regard as the left signal and which for the right signal and how does the input from the 3rd microphone combine to make the overall left and right signal. As you will tell, I have never used a mixer! Thank you!