Which MARC21 fields Identify the Bibliographic Material Type?

How is the "Material Type" for a title search defined? Which bibliographic information determines these facets:

Books (BK)

Journals (CR)

Computer files (CF)

Maps (MP)

Music (MU) Visual materials (VM) Mixed materials (MX)

These material types are defined by Library of Congress. See https://www.loc.gov/marc/bibliograph...e/bdintro.html .

These material types are identified from the bibliographic LDR position 6, 7.

For example, LDR Position 6 = a, Position 7 = a or c or d or m, the Alma Bibliographic Material is "BK", and Alma Material Type Term is "Book".

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