The in nomine is a genre of polyphonic composition unique to English consort music, originating in the Benedictus section of John Taverner's Gloria tibi Trinitas mass (written circa 1530). The composer uses the "In nomine Domine" plainchaint as a cantus firmus around which to weave counterpoint. Around the late 1560s or 1570s, multiple composers began to write such pieces, and the popularity persisted about a century, with the last period example composed by a youthful Henry Purcell. It is most associated with the viol consort, though a few keyboard, vocal, and lute in nomines are known. Typically, a high voice viol plays the in nomine plainchant in single breves, usually but not always entering before any other instruments.

Most of my transcriptions are Elizabethan examples. Later Jacobean in nomine compositions tended to be very complex and difficult pieces that show off the counterpoint skills of the composer.

See also:

• Wikipedia's In Nomine article
• The New Grove Dictionary of Music