These pages comprise a dictionary of terms relating to the pipe organ. Please keep definitions to a few sentences, and do not include pictures or sound clips. When more space is needed for a term, a new page can be created for it. Unda Maris - see Voix Celeste Unification [noun] a technique whereby many stops share a small number of ranks, with each rank being used on multiple keyboards at a variety of pitches. Theatre organs use unification heavily, but is not desirable on classical organs except as an extreme cost- or space-saving technique. Unit Orchestra Unit Organ Upper Lip Upper Rib