In Exodus 15:1, this signifies the glorification of the Lord on account of liberation from slavery. (Arcana Coelestia 8261)

In Psalm 27:6, represents what is spiritual from celestial love. (Arcana Coelestia 420)

Every affection of the heart has a tendency to produce singing, and so it will produce anything relating to singing. The affection of the heart is celestial, and the singing derived from it is spiritual. 'Singing' indicates the testimony of gladness from the affection for truth.

(References: Arcana Coelestia 418)