in nomine

Instrumental piece of the later 16th century for viols or keyboard, similar to the fancy or fantasia, but based on a plainsong melody used as a cantus firmus. The melody is that of ‘Gloria tibi Trinitas’, an antiphon for Trinity Sunday, which was used by John Taverner as the cantus firmus of a Mass with the title Gloria tibi Trinitas. Part of the Benedictus of this Mass, beginning at the words ‘In nomine Domini’, was arranged as an instrumental piece, and this seems to have suggested to other composers the idea of writing original instrumental pieces on the same cantus firmus. The last composer to write in nomines was Henry Purcell.