Hi Larry
I am embarking on a similar project,and find that most of the tunes I have are not worth keeping. Wheras, they are commercial files, they are the wrong genre for me, or too obscure.

As I see it, there is nothing gained by loading hundreds of songs on a SD card. I would think it better to bite the bullet and audition the ones likely to be used, and transer them in Technics format in the proper files.

The ones I audition load to my notation program(MidiNotate), and then saved as midi to be loaded to the KN. This way the Karaoke files display the lyrics on the keyboard.

Just my opinion.
Bernie