I also found a website that provided this explanation:

"Pentatonic songs ...are confined to do, re, mi, so, and la. According to Kodaly, Orff, and many other theorists on music education, this restriction could be of immeasurable benefit in teaching music students of any age to sing or play in tune..."

-snip-

Click HERE for more information.

That website has three different lists of copyright free songs:
one for songs using so and mi

one for songs using la, so, and mi

and

one for songs using la, so, mi, re, and do.

Sorry to again show my ignorance, but does that mean that some pentatonic songs are composed with less than 5 notes {like those in the first two lists?

I know-I know. I need to take a music class. But I would appreciate an explanation.

Thanks,

Azizi