I also sang Pergolesi's Stabat Mater - the soprano part. It is absolutely beautiful. I hope you have all listened to the 30-minute work of 12 songs, including solo pieces.
Baroque music is all about Affect and Pergolesi has used some interesting tools to convey emotions. to give us a sense of Mary's pain and desolation in the first piece Stabat Mater Dolorosa, Pergolesi uses many dissonances i.e. two notes that clash because they are too close to each other, like F-G, G-A, and then B-C in the first three bars (circled in the attached photo) between the Soprano and Alto singers. Dissonances are not pleasant to listen to and would normally be avoided in music, except when talking about visceral pain as here.
The key of this masterpiece is in F Minor, which was the key Baroque composers used for heavy, profound pieces with heart ache and a dark melancholy.
Solo pieces are absolutely beautiful and the end is also glorious, but my favorite is no:9 Fac, Ut Ardeat Cor Meum ("Make my heart burn") - a long, intricate, magnificent Fugue where the two Melodie's twist, turn, answer each other.
One last comment: Please listen to Pergolesi's Stabat Mater from a recent recording made by a specialist Baroque ensemble such as William Christie & Les Arts Florissants, Ricercar Consort, Christophe Rousset & Les Talents Lyriques. NOT Karl Richter or some other symphonic orchestra.
This is because these groups use Baroque instruments that sound quite different than the modern violin, celllo, and brass wind instruments. Aside from being made with different materials, some are actually different instruments like viola de gamba instead of cello. The are also all tuned to the Baroque pitch of A=415 , which is half a note lower than our modern A=440. This makes a big difference, as some of the notes are quite high and they sound shrill in our modern pitch.
Try this one:
Fac Ut at 21:30.