Composers who arrange or adopt public domain works can register their versions of the works to their PRO. We enable this with the selection of Arranger or Adaptor as contribution on a song. We follow the rules and guidelines provided to us by North American performing rights societies ASCAP and BMI (United States) and SOCAN (Canada).
Here are the rules:
Adaptor: The writer modified/adapted the lyric or text of a pre-existing Public Domain work
Arranger: The writer modified the musical elements of a pre-existing Public Domain work
Here are the guidelines:
You can select Adaptor or Arranger as a writer's contribution only if you've answered "Yes" to the question in the Song Details section, which asks "Is this song an arrangement of a song in the public domain?" You must also enter the title of the work. It's OK to enter "Traditional" in this field if the original song information is unavailable.
Here is how it appears on the Song page in the Catalog: