Here Monteverdi uses a primary group of three solo voices, adding a further five to produce a full eight-part texture for verses 2 and 6, the first half of verse 9 and the Gloria Patri. The three soloists sing, for the most part, in triple time and in imitative textures, but Monteverdi is careful always to allow the text to be clearly declaimed, and to punctuate it with cadences to mark the caesuras in the middle and at the ends of verses. When he uses the full texture of eight voices he allots it the same music each time—a rich harmonic progression in block chords. The reasons for his choice of one texture over another are sometimes easy to explain. For example, soloists are used for verse 1, in which the psalmist declares his intention to praise the Lord; the full texture is then used for verse 2, a statement that the works of the Lord are great. Similarly, a full texture is used for the first half of verse 9 to reinforce the striking statement ‘Holy and fearsome is his name’ and to round off the setting in the Gloria Patri, though here Monteverdi introduces a central section for three voices singing a line of his own invention extrapolated from the normal text—‘Semper gloria Patri et Filio et Spiritui Sancto’ ([Let there] always be glory to the Father and the Son and the Holy Spirit). His use of a full texture for verse 6 is more difficult to explain in terms of the text; he may have introduced it simply for the sake of musical variety.
from notes by John Whenham © 2003