Early music ensemble Musica Secreta’s new album Mother Sister Daughter celebrates women’s spiritual relationships and the stories they tell, but it also solves a mystery with an astonishing discovery.

As with our last two recordings, Lucrezia Borgia’s Daughter and From Darkness Into Light, this album has its roots in an archival puzzle. In February 2020, I was in the Archivio di Stato in Florence, looking for a pair of nuns. Not just any nuns, specifically Agnoleta Biffoli and Clemenzia Sostegni, who were both living in a Florentine convent in 1560. They were the recipients of a lovely, fragile hand-copied choirbook – the Biffoli-Sostegni manuscript – that contained enough polyphony for an entire year of worship in their choir. But which convent?

With the clues held by the music, I’d narrowed it down to two candidates: an elite house, San Jacopo in via Ghibellina, right in the middle of Florence, and a much poorer one, San Matteo in Arcetri, about a mile south of the city walls. For several years, I’d pursued Agnoleta and Clemenzia in the papers of the richer house: we’d even recorded from the manuscript and I’d made a film about it, standing in the doorway of what had been the convent’s church. When, on my last day, I finally ran out of books to look through with no trace of the women, I turned to the poorer house in despair.

Within minutes of opening up San Matteo’s records, I’d found both women, the dates they entered the convent, their dowries, and other information about their families and lives. So this priceless record of 16th-century convent music belonged not to the elite nuns of San Jacopo, but the humble, rural house of San Matteo. But what made this discovery so breathtaking was that San Matteo had also been the home of Suor Maria Celeste Galilei, Galileo’s daughter, who entered the convent in 1613.

Maria Celeste’s story hit the bestsellers’ lists in the early 2000s, as the subject of the book Galileo’s Daughter by Dava Sobel. Sobel translates Maria Celeste’s surviving letters to her father, which recount everyday life in the convent in vivid detail. Yet anyone who has read Galileo’s Daughter would think that San Matteo was a dour place, with very little to commend it: Maria Celeste – like most nuns, not allowed possessions of her own – often writes out of need, asking her father for the necessities of life. At one point she mentions almost in passing that she had been given the job of choirmistress. We might have once thought that she was simply leading plainchant. The discovery of a link with the Biffoli-Sostegni manuscript simply turns that idea on its head.

The high point in San Matteo’s liturgical calendar was the Feast of St Clare, founder of its order: it is a double feast, observed only in Franciscan and Clarissan monasteries and convents. The manuscript has a setting of the two Vespers services that is unique in two ways: because there are no other 16th-century polyphonic settings of vespers antiphons, and because they are composed for four very high virtuoso voices. Maria Celeste would have taught the novices to sing the 12th-century Franciscan Office on which they are based. We have recorded them with the chant antiphon and the doxology to give the modern ear a flavour of how they would have sounded to the nuns and their families, gathered in the external church listening to their daughters on the other side of the grille.

Even as the vespers antiphons are unique, one among them stands out, startling in its unusual sonic qualities. ‘Salve sponsa Dei’ – the Magnificat antiphon for Second Vespers, so the highlight of the two-day feast – is written in four voices in chant notation. The sound in performance is the sound of extemporised counterpoint, an ancient practice full of parallel motion and strange clashes. It is almost as if the 16th-century nuns were reaching back to their roots, and singing it makes us feel as if we, too, are collapsing the boundaries of time.

‘Salve sponsa Dei’ culminates two days of worship, during which the nuns sang Clare’s history: her life and death, her ascent with her sister Agnes into heaven, and the establishment of her order. They were, in essence, telling each other their origin story. It got me thinking about the ways nuns might use music to communicate with each other, and how music and liturgy taught them how to be women, particularly as many of them had been separated from their mothers at a relatively young age.

February 2020 was a scary time to be in Italy: as I left Florence the afternoon of my discovery, I was reading reports of terrifying sickness on the other side of the Appenines. A month later, Musica Secreta gave its last performance before all concerts were cancelled, and soon we were all to learn what it meant to be enclosed. I knew, though, that I wanted our next project, whenever it came, to be about women’s relationships and the stories they told about them. I went about finding, editing, and developing a programme of music honouring the Blessed Virgin Mary and communities of sisters – Catholic and Protestant – in 15th- and 16th-century Europe.

I also wanted the project to capture that sense of time collapsing, and of longing and separation, to bring listeners with us into the world of enclosed Renaissance nuns. The only way to do that was to commission a new work. In lockdown, Norfolk poet Esther Morgan’s poem ‘Half-Sister’ – written from the point of view of a woman enclosed in a dark house looking out at another woman in bright sunlight – had resonated strongly with me. So, I got in touch with Joanna Marsh, who I’d worked with a few years ago when she was writing for Stile Antico. She agreed to set the poem, coming up with the idea of juxtaposing Morgan’s words with a Renaissance text about nuns. I found her a sonnet written to commemorate the entry of a beautiful young singer into a Bolognese convent. The result is Joanna’s stunning ‘The Veiled Sisters’ – what a revelation it has been to us!

Mother Sister Daughter also reflects the Renaissance convent’s self-sufficiency: like our musical foremothers – supported by many generous donations from charitable funds, friends, and family – we have brought this album from inception to completion, releasing it ourselves when delays due to Covid made it impossible for us to go through the usual distribution channels with a record company. The album release coincides with our concert at King’s Place, London, Friday June 10, 7.30pm (kingsplace.co.uk); and a late-night concert at Stour Music, Friday June 24, 10pm (stourmusic.org.uk).