I am not familiar with the NABU Press edition available at
Amazon - from the description, it might contain the SCOTS MUSICAL MUSEUM plus a couple of others. or might only contain
the 2nd-6th vols of Musical Museum (Burns contributed starting
with the 2nd vol.) Perhaps you can contact NABU to get a definitive
answer. Also determine if this is a print-on-demand offering rather
than a printed book.

The 6 volumes were reprinted (in 2 volumes) in the 1960's by FOLKLORE ASSOCIATES, and more recently by SCOLAR and AMADEUS PRESS. The latter in used condition from around forty dollars.

Thomas.