Lasst uns erfreuen

"Lasst uns erfreuen"
German hymn tune
Oldest existing copy, 1625
English	Let us rejoice
Meter	88.88 with Alleluias
Published	Cologne, 1623
Audio, with original 1623 placement of the "Alleluia" phrases

"Lasst uns erfreuen herzlich sehr" (Let us rejoice most heartily) is a hymn tune that originated from Germany in 1623, and which found widespread popularity after The English Hymnal published a 1906 version in strong triple meter with new lyrics. The triumphant melody and repeated "Alleluia" phrases have supported the tune's widespread usage during the Easter season and other festive occasions, especially with the English texts "Ye Watchers and Ye Holy Ones" and "All Creatures of Our God and King".

The tune's first known appearance was in the 1623 hymnal Auserlesene, Catholische, Geistliche Kirchengesäng (Selected Catholic Spiritual Church-Songs) during the Counter-Reformation and the Thirty Years' War, and the oldest published version that still exists is from 1625. The original 1623 hymnal was edited by Friedrich Spee, an influential Jesuit priest, professor, and activist against witch-hunts, who is often credited as the hymn's composer and original lyricist. The 1906 hymnal was edited by notable composer Ralph Vaughan Williams, whose arrangement of the hymn has become the standard for English-speaking churches.

In the original 1623 edition, each eight-note text phrase was immediately followed by a four-note Alleluia phrase, all of which was followed by the final triple-Alleluia refrain, as in the audio sample at right. In English-language hymnals, the melody is usually a revised version, where before the final refrain the four-note Alleluia phrases occur in two pairs, shown at right from the 1625 German printing and below in modern rhythm and notation.

The verse consists of two repeated musical phrases with matching rhythms ("V", "v"), one using the upper pitches of the major scale and one using the lower pitches, and likewise for the Alleluia refrain ("R", "r"). Schematically, the structure of the original 1623 version can be represented as "vRvR VrVr RRr", and the revised 1625 sequence is "vvRR VVrr RRr", the tune thus achieving a "full and satisfying effect [built] with rare musical economy".