It requires skill to play even a single part with true legato between adjacent notes, with the appropriate size of break between repeated notes, and with natural phrasing. It requires more skill to play TWO such parts with true independence; that is, with the integrity of each part remaining intact. Even more skill is required to play THREE or FOUR parts or more with true integrity of line. The majority of the hymns in nearly all hymnbooks have four parts.
Achieving this independence in hymn playing is one of the greatest challenges to the beginning organist. It can be accomplished most efficiently by applying good practice habits. Do what it takes to gain full mastery of this important aspect of organ playing.