eBay might not be the most likely birthplace for a recording of 17th-century French harpsichord music, but that is exactly where Christophe Rousset’s latest project began. The French harpsichordist and conductor’s interest was piqued by a misidentified handwritten manuscript he spotted on the online auction site in 2004, whose true musical worth he only realised once it was in his hands. He became the proud owner of a collection of Baroque music that ranged from the famous to the unknown, from keyboard transcriptions of Lully opera excerpts to rare unpublished preludes. And the volume’s dedication posed a tantalising mystery: who was Madame Théobon?

She was, as Rousset’s elegant booklet note explains, an attendant to Queen Maria Theresa, wife of France’s King Louis XIV. That is, for a while, until a romantic dalliance with his royal highness led to her expulsion from the court and a new life as a lady-in-waiting to the Princess Palatine, the Duchesse d’Orléans. Royal intrigue aside, Rousset found little about Madame Théobon’s musical credentials. But assumptions can be made, not least that her place in society meant she would have known the finest...