Four years ago I wrote about a very interesting collection called Miserere, subtitled "Music For the Holy Week Litugy." It includes the famous "Miserere" by Gregorio Allegri, a setting of Psalm 51:

Have mercy upon me, O God, according to thy lovingkindness: according unto the multitude of thy tender mercies blot out my transgressions.

and a number of other appropriate works.  Here's the link to that post. Earlier today I discovered that the entire recording is now on YouTube. This link is to the first track. I think it will be followed by the others though you may have to use the "Watch On YouTube" button to get them.