All four vocal parts - SATB - divide in this work.
The CyberBass web site has each part highlighted on the sound track (the other parts are softer, in the background). Click on the following link and scroll down until you see your part.
In addition, there are audio links of complete recordings of this work. Once you have learned your vocal part using Cyber Bass, try singing along to these tracks:
Soprano 1 solo opportunity: "Agnus Dei" from Page 1, 3rd measure (throughout movement)
Mvt. III – page 21
Baritone solo opportunity: from page 21, measure 10 through square 11; page 25
Soprano solo opportunity: top of page 28
Mvt. VI – page 52 (3rd system)
O Man Greatly Beloved
& Nation Shall Not Rise Up against Nation
Baritone solo opportunity: bottom of page 52