Hi again:
My process includes a Yamaha PSR-S910 connected to a Boss BR-864 Digital Recorder. I set up each song by adjusting the style, changing or modifying volume of each "voice/instrument" and then recording to only one track. The vocal is taken directly into the 864 and the volume adjustments on each "instrument" used on the 910 are automatically overlayed onto the same track. I have sixteen track capability but prefer the one track method which is, essentially, a "live" recording. From the 864, I send the WAV file to my PC and edit the final song for minor volume changes, etc. Then I make a duplicate MP3 file and distribute copies to my other computers.
If I don't care for the first "take"... I simply record the whole thing again until I am reasonably satisfied. With an ancient voice like mine, my objective is primarily to get the gist of the song across with the idea that a real talent might want to do a cover, thus plugging me into the money stream.
I copyright and register each song via my publisher and ASCAP.
I hope this helps. There are better ways but I'm fairly prolific and can't afford professional demos.
Feel free to ask if I have not provided you with the answers you seek.
All the best,
Dave