I was first introduced to Sequentia's Hildegard with their Canticles of Ecstacy, which entirely fits the description of meditative music. Ordo, Hildegard's first opus, is an allegory, with different voices representing the virtures. Some are melancholic, wistful; others are meditative; still other voices triumphant. It is a rich blend of beautiful voices, but one caveat to the seeker of background meditative music. In the allegory, the voice of the devil (a rasping male voice quite suitable to the allegory) bursts out in several scenes to mock and frighten the virtues. The devil cannot sing, of course, so he shouts. This will disturb the casual listener expecting nothing but soothing sounds. It is historically appropriate but not necessarily everyone's cup of tea.