The music of Lent is one of the highlights of the season, nearly as evocative and dramatic as the event it portrays in song. Sometimes it seems like the profound emotion called upon the deepest and more well-developed talents of the best composers.
The difficulty of some of the best music is beyond the abilities of most amateur Church musicians, but fortunately we live in the age of music downloads, so that the best of it is available for private listening.
Let's leave aside Bach's Passions (and the overlooked settings by Telemann), and the unequaled magnificence of Orlando di Lasso, and instead look at a piece by Giovanni Battista Pergolesi, who lived only 26 years and wrote only a handful of works. His Stabat Mater packs an entire world of woven harmonies and melodies into a small but highly varied piece written for one high voice, one lower voice, and continuo (which can be a few strings or just an organ).
Having lived with this piece for many years, and even had the pleasure of singing a part of it publicly twice (once on the high voice, and once on the lower one), it is surely one of the great miniatures of post-Renaissance composition. Indeed, it was the most printed work of the entire 18th century. The only bad recordings are those in which the singers just try to toss it off (I'm sorry to say that Cecilia Bartoli is responsible for one of those!); in fact, the piece demands, utterly demands, all heart and soul.
There are two dozen or more available, and I'm not in a position to say which is best. However the one with James Bowman and Gillian Fisher has become a standard, though there are probably others that are more creative (the one I personally adore is out of print). There are recordings with all boys' choirs, male voices only, women's voices only, and others. So the best approach is to just buy two or three. You can't have too many, and if you haven't heard the piece, you are in for a real treat.
Pergolesi truly created a masterpiece. How many more might there have been? We don't know, but he left something for every Lent that followed his lifetime.
Update: Ok, I've found one that is just unmissable in every way (still not my personal favorite but a revelation in every way). It is by New College with Edward Higgenbotham, and it uses all boys - not those airy flat mobs we sometimes associate with boys choir but a small group of robust and vigorous voices that give this music the passion and sincerity and power that this music demands. There are 3 used copies available on Amazon. You are very fortunate if you can get one of these.