To record an MP3, merely follow the directions I posted at http://psrtutorial.com/L/REC/MakeCD.html
which will record a WAV file, then convert it to an MP3. Nothing to it.
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.)