Ivan B - Yes! That is it precisely!
Therefore, we should eventually have multiple doxy's. With their SOURCES and dates cited.
For example there are four Doxology in The Hymnal for Worship and Celebration Word Music, Waco, Texax, 1986.
All have the same well-known words.
1. The one in the DT, #625 TEXT: Thomas Ken, MUSIC:German Psalter, 1551, attributed to Louis Bourgenis and the notation (OLD HUNDREDTH L.M.) 4/4 time
2. The one I kown #624, same sources but 2/2 time with extended phrases.
3. #626, MUSIC: Jimmy Owens, 1972, Lexicon Music
4. #627, A Doxology Canon, MUSIC: Jimmy Owens, 1986 Word Music.
What does "Old Hundredth" refer to?