If you like this piece, then look for the Barber arrangement for unaccompanied chorus (acappella) recorded by Robert Shaw. This music with voices in place of strings is one of my favorites.
It is titled "Agnus Dei", and is available on a Robert Shaw CD titled Evocation of the Spirit. The Tower Records link that includes samples to listen to is:
http://www.towerrecords.com/product.asp?pfid=1095833
If you did not know, this adagio is originally the second movment of a String Quartet by Barber. It is also fun to listen to in its original version. I have a recording by the Emerson string quartet.