A general description of field 047 is available at:
The possible two-letter codes are listed at:
This is a keyword search on a field which helps to locate examples of forms of musical composition in scores and sound recordings which other searches might not have turned up. It is suitable only as a supplement to other searching methods, because the bibliographic catalog records for items confined to one form place the code not in a field 047, but in a fixed-length area of the record which is not accessible to this kind of search!
This example finds ragtime music: