The sole score of this Mass setting based upon Sarum chant was lost soon after its composition in the mid-60s.  When it surfaced in 2004, I found the discipline of canonic play within an entirely white-note palette (the "total diatonic", neither modal nor tonal) produced such intriguing textures and sonorities that I revized it from top to toe and gave it over to op. 4 (thus displacing incidental music for Eliot's Sweeney Agonistes, which had also, earlier, been worth the trouble of revizing and re-copying).