Just purchase an inexpensive splitter cable that would send your audio output of the keyboard to the PC's audio input, then download Audacity at
https://www.audacityteam.org/ and you're on your way.
Good luck,
Gary
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)