By Pallab Ghosh
Science Correspondent, BBC News
The Lituus is a straight horn measuring 2.4m with a flared end
New software has enabled researchers to recreate a long forgotten musical instrument called the Lituus.
The 2.7m (8.5ft) long trumpet-like instrument fell out of use some 300 years ago.
Bach's motet (a choral musical composition) "O Jesu Christ, meins lebens licht" was one of the last pieces of music written for the Lituus.
Now, for the first time, this 18th Century composition has been played as it might have been heard.
Researchers from the University of Edinburgh carried out the study, which was funded by the Engineering and Physical Sciences Research Council (EPSRC).
Performed by the Schola Cantorum Basiliensis (SCB) the Lituus produced a piercing trumpet-like sound interleaving with the vocals.
Until now, no one had a clear idea of what this instrument looked or sounded like. But there are several depictions of similar instruments being played throughout Europe for centuries.
The team at Edinburgh University developed a system that enabled them to design the Lituus from the best guesses of its shape and range of notes.
The result was a 2.7m (8.5ft) -long horn, with a flared bell at the end.
Hard to play
It is an unwieldy instrument with a limited tonal range that is hard to play. But played well, it gives Johann Sebastian Bach's motet a haunting feel that couldn't be reproduced by modern instruments.
The software was originally developed by researcher Alistair Braden to improve the design of modern brass instruments.
But Dr Braden and his supervisor Professor Murray Campbell, were approached by a Swiss-based music conservatoire specialising in early music, the Schola Cantorum Basiliensis, to help them recreate the Lituus - even though no one alive today has heard, played or even seen a picture of this forgotten instrument.
SCB gave the Edinburgh team their expert thoughts on what the Lituus may have been like in terms of the notes it produced, its tonal quality and how it might have been played.
They also provided cross-section diagrams of instruments they believed to be similar to the Lituus.
The reconstruction could have been manufactured in Bach's time
"The software used this data to design an elegant, usable instrument with the required acoustic and tonal qualities," says Professor Campbell.
"The key was to ensure that the design we generated would not only sound right but look right as well."
He added: "Crucially, the final design produced by the software could have been made by a manufacturer in Bach's time without too much difficulty."
SCB has now used Edinburgh's designs to build two identical examples of the long-lost instrument.
Both were used in an experimental performance of "O Jesu Christ, meins lebens licht" in Switzerland earlier this year.
"Sophisticated computer modelling software has a huge role to play in the way we make music in the future," comments Professor Campbell.
The software also opens up the possibility that brass instruments could be customised more closely to the needs of individual players in the future - catering more closely for the differing needs of jazz, classical and other players all over the world.