Full text: 
Cantabo domino in vita mea
Fulltext source: 
E-L MS 8 fol. 121r. Link to this page in the Leon Antiphoner: AND Madrid, Real Academia de la Historia, Aemil. 56, fol. 48v.
On this chant see: RANDEL Don M., An Index to the Chant of the Mozarabic Rite, Princeton University Press, 1973, p. 453.