Unser Mund sei voll Lachens (May our mouth be full of laughter),[1] BWV 110, is a church cantata by Johann Sebastian Bach.

Bach scored the work festively for four vocal soloists, a four-part choir and a Baroque instrumental ensemble of trumpets and timpani, transverse flutes, different kinds of oboe, strings and basso continuo including bassoon.

The song of the angels is based on the Christmas interpolation Virga Jesse Floruit of his Magnificat in E-flat major, BWV 243a.

[1] In 1723, his first year in Leipzig, Bach had composed no new cantata for Christmas Day, but revived Christen, ätzet diesen Tag, BWV 63, on a text of free poetry without any biblical or chorale content.

In 1724, his second year, he composed three chorale cantatas for the three feast days, beginning with Gelobet seist du, Jesu Christ, BWV 91.

[1] In his third year, Bach used a cantata text by Georg Christian Lehms, which was published already in 1711 in Darmstadt in the collection Gottgefälliges Kirchen-Opffer.

[2] The librettist began with a quotation of two verses from Psalm 126 which deals with the hope for delivery of Jerusalem, "When the Lord turned again the captivity of Zion, we were like them that dream.

[1][3] Bach led the Thomanerchor in the first performance in the morning of Christmas Day in the Nikolaikirche, repeated in the afternoon in the Thomaskirche.

[5] Some Bach scholars believed that the cantata was written in 1734 for the end of the War of the Polish Succession,[6] but the discovery of the printed text showed that it was not related.

The opening chorus on psalm verses is an adaptation of his overture to his fourth Orchestral Suite in D major, BWV 1069.

[4] The laughter mentioned in the text is "often made quite graphically audible", as the Bach Scholar Alfred Dürr words it.

Gardiner chose this cantata in one of three Christmas concerts to conclude the endeavour of a full year, and notes the first movement's "marvellous rendition of laughter-in-music" and "innate elegance and lightness of touch".

[1] The alto aria, "Ach Herr, was ist ein Menschenkind" (Ah, Lord, what is a human being),[11] is accompanied by a solo oboe d'amore that "expresses wonder about the nature of man" and God's interest in him.

[1] The Bach scholar Klaus Hofmann relates the choice of the oboe d'amore to the answer to the singer's question "Why do you do all this for man?

[10] The music is based on the Virga Jesse floruit from the Magnificat, changing the vocal lines to the different text but retaining the "essentially lyrical character".

[13] Bach set the same tune again to close Part III of his Christmas Oratorio with another stanza from the hymn, "Seid froh, dieweil" (Be glad, therefore).