For an update on simpler polyphonic pieces.
Panis Angelicus Casciolini or Baini - this is the modernish one. Greg’s choir has an older one.
Jesu Rex Admirabilis Palestrina - this is an awesome, must have piece for every choir
Ametur - easy 3 part motet in honour of the Sacred Heart of Jesus by Australian MSC priest.
O Sanctissima 3 part arrangement attributed to Beethoven
Canons (also known as Rounds)
Tantum Ergo The one Fr Popplewell wrote and taught at the legendary BXVI Homeschool Camp of 2017.
Jubilate Attributed to Michael Praetorius
Magnificat - transcribed from students memories
Other stuff I haven’t tried yet
I keep coming across so many more pieces that I’d love to try one day, so I’ll add these ones in here for the future.
Ravanello’s 3 part motets written for small choirs
Kevin Allen’s 3 part motets (I bought the book from Lulu - 3 copies, but there’s a hurdle learning new stuff, even though this link has practice recordings)
Richard Dering was a composer in the court of King Charles and he wrote Cantica Sacra for 2 and 3 voices with Basso Continuo. I’m in the process of getting my head around what Basso Continuo means - I get the impression it’s the base for an organ improv accompaniment thing. Anyway, this could be a source of more pieces.