Each hymn is authored in 3 or 4 manners:
Music (melody)
Setting (also known as arrangement or harmony)
Words (original language)
and possibly translation

Each of these four are indicated specifically for each hymn; listed on 
the score sheet and in the abc source file.

The task of assembling and bringing the Open Hymnal into a single 
consistent entity from various sources is primarily the work of:
brian dot j dot dumont at gmail dot com