If you are using the line out of the computer for some type of presentation or show and it is only singular mono(only one output)then you wont have the capability of panning left to right unless you pan the channels of each mike L & R respectivily on a mixer and send that output directly to a stereo amplifier, bypassing the computer audio output which you can then patch into the mixer as well. This method will not send your voices through the computers card.
If you want to send audio into the computer from your voices and you keep your mono card you could do that,and there are numerous software programs that will add effects to your voices.I recently read about a dedicated laptop music computer designed specifically for musicians using midi and audio live. Anyone else hear much about that?
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Smitty