The motet Etans Assis is a setting of the French text of Psalm 137, an Israelite lament expressing the grief of captivity and exile in Babylon. The piece opens with a polyphonic section beginning with a fugal setting of the text steeped in rich, poignant chromaticism.  The rivers of Babylon are painted through fluid eighth note figures in the subject; the weeping and tears of the Israelites are represented by a steadily falling countersubject with bitter dissonances against the subject. Babylon itself is represented by the key of E minor, to which the subject modulates, while A minor, the opening key of the piece, is representative of Zion. The bridge section of the fugue (‘we remembered Zion’) is based on a chromatic motive with a wandering character that finally leads back to the opening key.

The text about the willows in the midst of Zion is set to two canonic sequences in contrary motion which branch off into soprano and alto duets, all meant to resemble the branches of trees when seen on the page.

The hanging of Israelite harps is depicted in the next section with a number of suspensions between entering voices. Two recitatives follow, indignant declamations by the bass and tenor: ‘those who made us bow demand joy, and those who took us captive demand that we sing!’ The strings reply, commenting in quick, Carrisimian imitative sequences that start joyfully enough, but end in slow, pained cadences. The following section is a ground in E minor over which an exchange ensues between two choirs: five singers as Babylonians, and three as Israelites. The melodic languages of these two groups are vastly different: the Babylonians sing lines of a joyful character, coupled in thirds, confidently in the new key, and with the dotted rhythms befitting conquerors, while the three Israelites respond with the same slow, lamenting chromatic language of the opening fugue, asking how they can sing the songs of their God on foreign soil (or over a strange ground).

The final section, a slow chorus, expressing the Israelites’ fervent wish never to forget Jerusalem. The end of the piece never returns to its opening key, just as the Israelites cannot return to their native land.