Arvo Part seems to bring an otherworldly, breathtaking quality to choral and symphonic music. If you're unfamiliar with his work, this is a great place to start. I especially love the uncompromising rejection of Big Music: you aren't going to hear one blaring brass orchestral piece on this album, which is a fresh, freeing change for classical fans. He seems to understand the fact that quality is far more satisfying than quantity, and that skill far outstrips volume.
You're going to notice that a few pieces appear more than once. (Fratres, Summa) Part's music is so multilayered that different presentations produce far different reactions, and it's fun to find a favorite. In my opinion, Summa for String Orchestra is the most beautiful rendition of it. Somehow, giving a choral work to a group of violins takes the music out of the church and into the pasture. Fratres for String Orchestra and Percussion is an incredible piece, telling a powerful, nebulous story in a gentle and careful way.
Tabula Rasa is really its own world, and has an apt title: it reminds me of a tableau on top of a mountain, a soaring, alien musical landscape. The 'prepared piano' in it sounds profound and strange, like a completely different instrument. Dim the lights, and blast this one as loudly as you can.
If you're looking for more, more is out there. The violins are played sweetly in this version of Tabula Rasa: a more uncompromising, stark version lies in Gidon Kremer's Silencio. The piano is emphasized a bit more, and the recording itself seems to highlight the extraordinary high notes from the violin. If you enjoy Tabula Rasa, I think that it is worth getting that version to understand how the piece can be played differently. Also, there exists an album called Fratres played by the Flanders Orchestra where the most interesting versions of Fratres can be found, in my opinion.