Gaudete -symphonic wind dectet/bass

Gaudete "rejoice [ye]" is a sacred Christmas carol, thought to have been composed in the 16th century. It was published in Piae Cantiones, a collection of Finnish/Swedish sacred songs published in 1581. No music is given for the verses, but the standard tune comes from older liturgical books. 
It is sometimes entitled Gaudete, Christus est Natus. 

British folk rock group Steeleye Span had a hit in 1973 (No. 14, UK singles chart) with an a cappella recording of the song. Guitarist Bob Johnson had heard the song when he attended a folk-carol service with his father-in-law in Cambridge, and brought it to the attention of the rest of the band. (Unlike the album version which fades up slowly and fades down slowly, the single was at the same volume for the entire length of the song.) This single is one of only three top 50 British hits to be sung fully in Latin