Here's another update on this song, which provides a new clue to where the chorus came from. Wendy's (Winifred L. Holt) son Phil just dropped off three of her song notebooks and I was able to find her original notes on "De Massa ob de Sheepfol'". Wendy did attribute the words to J.M. Whyte and the lyrics she wrote down came from a Miss McLean and included the chorus as follows:

For de Massa guards de sheepfol' bin
An' he wan's to know, "Is my sheep come in?"
An' he's callin', callin'
Callin' softly, softly callin'
For dem all to come gadderin' in.

Other than that the words are very close to the original poems as described above. The words apparently came with the familar tune but there was no musical notation other than suggested keys for group singing.

Charley Noble