According to 16th-century clerics, convent polyphony was dangerous, liable to lead nuns into vanity and other wickedness. Listening to the sensuous contrapuntal writhings and twinings, the ecstatic, rapturous beauty of these motets – possibly by Lucrezia Borgia’s daughter Leonora d’Este – you wonder if they didn’t have a point.

The motets are from the Musica quinque vocum motteta maternal lingua vocata – the earliest published collection of polyphony composed for nuns. As piece after piece of graceful, equal-voice counterpoint unfolds, what’s striking is how progressive and sophisticated the style is for the 1540s, its smooth consonance spiced with occasional hits of chromaticism, its long lines embellished with little gilded flickers of ornamentation.

With voice-parts confined to a two-octave range the risk is of a lack of scope. But thanks to careful deployment of solo and collective forces – the professional singers of Musica Secreta and excellent amateurs of Celestial Sirens – and judicious use of bass viol and organ, there’s enough delicate variation to keep things interesting.

Haec dies is rejoicing, kept from all-out ebullience by its dark modality, while the filmy Hodie Simon Petrus, with its imitative upper voices and lace-like detailing, unfolds in rapt arcs. The longest work, Angelus Domini descendit, is a musical meditation whose impetus never sags. But whether it led convent visitors to thoughts of God or those of a baser kind it’s hard to say.