This is one of my favorite of Giovanni Gabrieli’s large works. The motet is set in sixteen parts and was published in the Sacrae symphoniae… liber secundus in 1615. The work uses the texts from the third and fourth responsories for Christmas Matins interspersed with other passages. This motet is divided into various parts. It opens with a instrumental sinfonia for two choirs of instruments in a low ambitus. Then a wide section (it occupies most of the work) of imitative vocal duets, trios and quartets.
I believe that this section must be the reconstructed edition made by Hugh Keyte, with a reworking of the inner sections of this part with reconstruction of instrumental lines. This section is extremely rich, with a permutation of textures and rhythmic variety in the text repetitions, accompany by a sort of continuo. This development of thin textures continues until the start of the “O magnum mysterium” section.
In this section, after a brief rest, the tutti states “O great mystery” with an almost dazzling sonority and audacious block chords progressions. This is particularly magnificent at “et admirabile”. The final Alleluia section is to me one of Gabrieli’s most extrovert passages, unfolding with the magnificence of the so-called Venetian style.