In the Dominican Missal, the Sequence Laetabundus, is still permitted for the Third Mass of Christmas, the Epiphany and Candlemas.
This was once the most famed of Nativity sequences and it was attributed to St. Bernard of Clairvaux (d. 1153). It was proper to the Praemonstratensian liturgy and was especially popular in England and France. It is written in rhymed stanzas and thus differs from most early proses.
This Sequence is believed to survive today only in the Dominican liturgical books and the recording above is from the Dominican priory of the Holy Spirit (Blackfriars) in Oxford. The Latin text and its English translation may be found here and the music here.
The above video was originally posted at 'Godzdogz'.