Science aids the quest for Bach’s mysterious horn
A recent collaboration between musicians and scientists has resulted in the construction of a musical instrument, which may be the mysterious “lituus” written for by J. S. Bach. Bach’s funeral motet ‘O Jesu Christ, meins Lebens Licht’ (BWV 118) is thought to have first been performed in 1736-7. Bach’s score calls for two “litui” along with other more common instruments.
Musicological research conducted at the Schola Cantorum Basiliensis; Basel, Switzerland (http://www.scb-basel.ch [German language]) proposed that the “lituus” written for by Bach may have been a long wooden natural instrument, sounding somewhere between a trumpet and an alphorn, and playing a series of natural harmonics. An initial design of the bore profile was created from interpolated measurements of a natural trumpet and a straight büchel (a wooden alphorn-like instrument). The challenge faced by scientists at the Musical Acoustics Laboratory in Edinburgh (https://www.acoustics.ed.ac.uk) was to improve this initial design for the lituus and produce an instrument with the appropriate sound, pitch and timbre. This bore profile was optimised in Edinburgh using specialist software developed by Dr Alistair Braden during his PhD at the University of Edinburgh.
Providing an integrated software package which allows for the design, testing, and optimisation of brass instruments, the Brass Instrument Evolution Software (BIES) models the behaviour of multi-modal acoustical pressure waves within a given instrument bore profile. The software was used to set target input impedance peaks for the lituus, modelled computationally, which then produced a design for the instrument that would play in tune. Two litui were built from the optimised design and were played in a concert at the Schola in Basel and subsequently here in Edinburgh. The sound produced by the instruments is very similar to how researchers believed they may have originally sounded; sounding neither like a trumpet, nor an alphorn, but a combination of the two.