In convertendo Dominus (When the Lord turned [the captivity of Zion]), sometimes referred to as In convertendo, is a setting by Jean-Philippe Rameau of In convertendo Dominus, the Latin version of Psalm 126, (thus numbered in the King James Bible, number 125 in the Latin psalters). It is listed as RCT 14 in the Rameau Catalogue Thématique of Sylvie Bouissou and Denis Herlin.
In convertendo is one of the four surviving church works of Rameau's early career, dating to the period 1710-1714 when he was working in Dijon or Lyon; other similar works are known to be lost. The work was rewritten and updated in style for a performance at the Concert spirituel in Paris in 1751. The manuscript of the 1751 version, now in the Bibliothèque nationale de France, was originally in the collection of Jacques Joseph Marie Decroix , the lawyer and friend of Rameau who built a large collection of his manuscripts after the composer's death. The motet is scored for soloists, choir, strings and woodwind, and includes, after the fourth verse, a verse not in the original psalm, Laudate nomen Deo cum cantico (Praise the name of God in song). The final verse is composed to include a fugue which, in the opinion of Reiner E. Moritz, "can stand direct comparison with ... Rameau's contemporary J. S. Bach".
The Latin text is given below alongside the translation of the psalm in the King James Bible. The text in square brackets is not in the original psalm.