Music Library Association Best Practices for key of representative expression

Routinely record the element in authority records if used as a component of an access point. Record the element in other cases if readily ascertainable.

Do not record the element in bibliographic records; instead record Expression: key of expression (even if the key actually expressed in the manifestation described is identical to that of the representative expression).

Until further guidance is developed, this element should be considered to apply only to music conforming to Western tonal harmony. Other pitch organization systems, including non-Western systems, Western ecclesiastical modes, jazz modes, atonal pitch systems, pentatonic or whole-tone systems, etc. should be considered out of scope for the time being.

In MARC: Record as a structured description using field 384 subfield $a for single works.

See examples in MARC format: key of representative expression

Also consider this condition to apply single works made up of consituent part works.

In MARC: In authority records for works with consitutent parts, record a note on the keys of the parts as an unstructured description if deemed useful for identification or access.