Your links don't seem to work from here, Q. But in any case, the American Memory definitions of ephemera are not quite the ones generally used by people studying songs. Most of the AM categories are irrelevant to song studies as they were not used to disseminate songs. On the other hand, forms that WERE used for songs go unmentioned; they do not mention slips or garlands, for example.

They have also conflated "broadside" and "broadsheet" into one category (which is pretty reasonable).