A key_signature record represents the data of a MusicXML key element. One or more key elements may appear within an attributes element. All of the key_signature records within an attributes element join to table music_data, music_data_type attributes, foreign key attributes_id.

The key_signature table is single-inheritance with discriminator column key_signature_type>. Possible values of key_type are:

• traditional key
• non-traditional key

The key_type value depends on the presence of traditional-key or non-traditional-key elements.

Each key-octave subelement is a record in table key_octave, foreign key key_id.

A traditional key stores its element values in fields cancel_fifths, fifths, and key_mode for elements cancel, fifths, and mode, respectively.

Multiple non-traditional key element groups store their values in the non_traditional_key_type table. The key-step, key-alter, key-accidental element text values are stored in fields key_step, key_alter, and key_accidental, respectively. The key-accidental element's smufl attribute is stored in field key_accidental_smufl.