I absolutely adore this set and frequently listen to both, often loud; at first the Arab muwashshah and the one Jewish piyyut were so foreign, I did not know what to make of them. But every time I listened, it was like peeling an onion: layer upon layer of subtle sounds and poetry. Some of the works are dignified and haunting (the Christian Cantar, Cantio, etc.), some belong to a lost secular tradition (the recited 'Poema de Mio Cid'), some frankly sensual and rich ('Ma li-l-muwallah' of Ibn Zuhr). And I was pleasantly surprised to see the great poet Yehuda ha-Levi's work set to music.
Authenticity is the key: these are accomplished scholars as well as musicians, piecing together fragments of foreign manuscript codices with the appropriate modern Moroccan prototypes, and creating period instruments. As another reviewer mentioned, most of the vocal stylings, particularly in the Jewish and Arab pieces, are not operatic, but rather, flat and nasal (but complex and fluid), and thus believable. The Christian interpretations are more 'classical', and utterly exquisite. Pronounciation in each represented language (Hebrew, Arabic, Latin, Gallo-Portuguese, Spanish) is comprehensible and historically accurate.
I also appreciated the scholarly liner notes, which broadened my understanding of the music. I've spent much time comparing the Arabic, Jewish, and Latin to the English translations and transliterations.
This period of Jewish/Muslim/Christian relations was perhaps one of the most fruitful eras in history, and one of rare co-operation. Scientific, religious, philosophical and cultural achievements reached an all to brief apex of harmony. Rarely does one find such an extraordinary portrait of a Golden Age as represented here in the blend of musical styles.