Not only is the PC Mic input mono, it is also scaled for much more sensitivity.

Typical AC Audio output of a keyboard is consumer Line Level, on the order of 2V.

Typical Mic Level is on the order of 50 to 200 milliVolts.

A milliVolt is 1/1000th of a volt.

As you can see, attaching the Line Level output of the keyboard to the Mic Level input is a mismatch on the order of twenty orders of magnitude and at least would result in overdrive of the audio and clipping, and could possibly damage the mic preamp input over time as well.

An aftermarket sound device, USB if laptop, would be the way to do this. On top of having the proper Line Level inputs, it would have two, stereo L & R, and most keyboards output a stereo signal, much better for recording purposes.


--Mac