The lack of direct evidence describing contemporary performances of the Cantigas means scholars must draw upon circumstantial evidence to ascertain possible performance practices - a treacherous minefield. From this, a number of plausible options seem to emerge (depending on context) including the one presented here by Jordi Savall: a sizeable ensemble with various instruments.
Alongside the Cantiga MSS illustrations of musicians (all art historians seem to regard the miniatures as 'real life' depictions), near-contemporary accounts survive of large pilgrim ensembles at Spanish shrines, most famously the 12th century Codex Calixtinus (although seemingly unrelated because of its earlier date, this describes a large multi-instrument pilgrim ensemble [like those depicted in some Cantiga illuminations] at the altar of St James at Compostella - a shrine mentioned in certain Cantigas, e.g. CSM 26 and CSM 253. Pilgrims and shrines feature in a number of Alfonso's Cantigas, like CSM 163 'Pode por Santa Maria' [track 8 here], CSM 49, CSM 167 etc...).
This may shed light on Alfonso X's will, which stipulates continued performance of the Cantigas in Seville Cathedral after his death. Additionally, CSM 8 (about a minstrel praising the Virgin) appears in Gautier de Coinci's 'Miracles de Nostre Dame' - the likely inspiration behind Alfonso's collection - where it is followed by a description of some sort of devotional music involving voices and instruments ('...la clere vois plaisant et bele, le son de harpe et de viele, de psaltere, d'orgue, de gygue...') [R.e. all the Cantigas de Loor are devotional.]
Neither Savall nor Jesus Martin Galan (author of the booklet notes) discuss performance practice, and the apparent plausibility of the results - at least, in a devotional context - is perhaps in part accidental (given some of Savall's performance decisions of 15th century Cancionero songs...).
Yet it is difficult to imagine the multi-force approach being better done. Improvisations are concise, and the interpretations 'European'. Alongside some wonderful singing (mostly tutti, but with noteworthy solos from Montserrat Figueras and Mercedes Hernandez [track 5], and Lambert Climent and Francesc Garrigosa [track 8]), the instrumental playing is superb and the line-up includes directors of other major early music ensembles (Andrew Lawrence-King [The Harp Consort], Pedro Memelsdorff [Mala Punica], Crawford Young [Ferrara Ensemble], Markus Tapio [Retrover] and Alfredo Bernadini [Zefiro]).
2 other recordings of this repertory worth checking out are:
1. Cantigas de Santa Maria: Eno nome de Maria, Johanette Zomer + Antequera (Alpha 501) - perhaps the best exploration of Moorish influences in Alfonso's court.
2. Sequentia performs Vox Iberica III by El Sabio (DHM), Sequentia / Benjamin Bagby and Barbara Thornton (DHM 05472-77173-2) - mostly large, a cappella forces.