I've heard the name here and there but I don't know much about Robert Parsons (1535-1572), an English composer who was apparently an influence on William Byrd. I'm quite sure I had never heard his music, until yesterday, when this blog posted a notice.
So: have a listen to this amazing treasure (gasp, it's so beautiful), Parsons's Ave Maria. Here is the score for music geeks. The harmonies and modulations seem intuitive enough to be managed by amateur choirs. When you hear music like this, you can't but stand in disbelief that this material was ever allowed to go unsung and be so neglected, much less displaced by...well I'll stop there and let the music speak for itself.