He's not the first composer to attempt to complete it, but Robert Wiremu's arrangement of Mozart's unfinished Requiem is possibly the most imaginative.
The Auckland-based composer and singer has taken Mozart's score and refashioned it with a new narrative, putting it at the bottom of the world on the slopes of Mt Erebus.
For New Zealanders, that Antarctic volcano is forever associated with the 257 people who died when an Air NZ scenic flight crashed into its lower slopes in November 1979.
Robert told Three to Seven host Bryan Crump he imagined a scenario after the disaster where a portable music player might still have been playing following the impact.
"The premise for my use of the Requiem is this: I imagine, with no evidence whatsoever, that one of the passengers may have had a Walkman... Inside the Walkman was a recording of Mozart's Requiem. As damaged as it was, the notes are carried into the Antarctic air by the winds around Ross Island, up Mt Erebus, across from the continental mainland, over the icebergs of the surrounding seas, and the ice bridge."
"These notes are often recognisable as Mozart, but not always".
Robert has scored his arrangement for a chamber choir – in the case of its debut, Voices New Zealand – and a small chamber orchestra of seven players. Reimagining Mozart will be performed in six centres around New Zealand between 13-29 October, including a performance on 28 October as part of the Nelson Arts Festival.
There is, as always with Mozart's Requiem, the question of how to finish it. Franz Süssmayr recycled material from the Requiem itself. Robert went to another Mozart source, his last completed choral work, Ave Verum Corpus.
In choosing that path, he's brought the story back to New Zealand, as it's dedicated to Robert's friend, colleague and former Voices NZ singer, Helen Acheson, who died suddenly earlier this year.
"[Helen] was meant to be involved in this project, and whom we miss dearly. She was a wife, mother, a facilitator, a problem solver, a muse. This arrangement of Ave Verum Corpus begins with 43 bell tolls, one for each year she shared her light with us."
In so choosing, Robert has made his arrangement of Mozart's Requiem more than a completion, or even a memorial to the Erebus Disaster, but a meditation on sudden loss itself.