Just go buy some chanting CD's. Anything called "Gregorian Chant" is what you're looking for.. Here are some of my other favorites:

• Harmony of the Soul
• Maitri Vihar Monastery
• Sacred Ceremonies: The Ritual Orchestra and Chant
• The Benedictine Monks of Santo

All good relaxing chanting stuff. If you're looking for other relaxing stuff, I would also highly recommend anything by Kitaro.

-marius