A Dictionary of Music and Musicians/Invitatorium
INVITATORIUM. A species of Antiphon, appointed, in the Roman Breviary, to be sung, at Matins, in connection with the Psalm 'Venite exultemus Domino.' Anglican Ritualists sometimes apply the term, Invitatorium, or Invitatory, to the 'Venite' itself; but this use of it is incorrect. It consists of short sentences, sung before, and between, the Verses of the Psalm; and sometimes gives rise to very elaborate complications in the text and music.
[ W. S. R. ]