Prince Leopold was Bach's patron in the small town of Cöthen, where the young composer arrived to take up the post of Capellmeister in 1717. Leopold was a cultured and genial employer, who, according to Bach, "both knew and loved music". And though the composer only stayed until 1723, his Cöthen years were creatively productive. Much of Bach's music from this period has been sadly lost, including the sequence of pieces written in 1728 to mourn Leopold's sudden death at the age of 34. A libretto, by Bach's colleague Christian Henrici, survives. This has enabled academics convincingly to argue the case for a reconstruction, using movements from the St Matthew Passion and the recently completed Trauer-Ode for the Electress of Saxony. Bach often recycled his own works, and it's possible that the suddenness of the funeral commission prompted such a practical solution.

The booklet reveals where individual arias and choruses have come from, and the finishing touches are provided by conductor Andrew Parrott's newly composed recitatives. The use of one voice per part never sounds anaemic and the singers' crystalline clarity is a joy to the ears - little surprise when you reflect that Parrott recorded one of the best small-scale versions of the B Minor Mass in the 1980s. What's most important is that the work sounds like a real, finished work, not a speculative completion. It's beautifully recorded with good notes.