The short expressive piece 'Ah, mine heart' sets a fifteenth-century penitential poem of great fervour. Jackson alternates a refrain in a simple plainsong style with more passionate, homophonic verses, to powerful effect. A setting of the Trinity Sunday text with achingly pure and fluid melodic lines feature throughout, imbuing the piece with characteristic clarity and luminosity. The change to A major for 'Trinitati in Unitate' is radiant, as is the final section, in which the choir divides into eight parts to proclaim the glory of the Trinity. Uplifting and powerful, this is rewarding music for committed choirs. Composed for the Feast of Corpus Christi, 'O Sacrum Convivium' has a poise and beauty rare in choral music. Jackson uses the full sonic opportunities offered by the divided scoring, moving effortlessly from controlled meditation to ecstatic fervour, all delivered with absolute belief and clarity. The anthem 'Now I Have Known, O Lord' is set to a text by the 10th-century Sufi mystic, Al-Junaid. For the most part, the mood is intimate and introspective; intertwining, whispered melodies, sometimes in free time, alternate with quiet homophony. There is a moment of soaring, unrestrained ecstasy towards the end of the piece before it draws to a hushed conclusion. Suitable for a variety of occasions, this is beautiful, challenging music for serious choirs.