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The Quest for Bach's "Lituus"
*** Lituus in the news! *** The lituus is featured in an article on the BBC news website and on the EPSRC website as a press release. An article addressing the musicological reasons behind this project can be found at De Swaen.
What is Bach's lituus?
Johann Sebastian Bach's (1685 - 1750) evocative funeral motet 'O Jesu Christ, meins Lebens Licht' (BWV 118), appearing in two versions, is thought to have first been performed in 1736-7. The first version of Bach's score calls for four voices, cornett, three trombones, and two litui, and the second version for four voices, strings, bass continuo, and two litui. But what exactly is this "lituus" that Bach refers to?
Work conducted by researchers at the Schola Cantorum Basiliensis (Basel, Switzerland) indicates that the lituus may have been a long wooden natural instrument, sounding somewhere between a trumpet and an alphorn, and playing a series of natural harmonics. It is, however, not to be confused with the Roman lituus; a military instrument which unfortunately has too wide a bore profile to play all the notes Bach demands in his score. The performance in the YouTube video by the Bach-Collegium Stuttgart (right) does not use litui, but instead uses what appear to be alto horns.
Designing the lituus
Scientists from the Musical Acoustics Laboratory at the University of Edinburgh were contacted to collaborate on the design process. Provided initially with a bore profile formed from interpolated measurements made for a Nagel trumpet (17th Century Nuremberg natural trumpet in D flat) and straight buchel (wooden alphorn-like instrument), theoretical models were constructed and analysed using specialist software recently developed at the University of Edinburgh.
From the findings of musicological research at the Schola Cantorum Basiliensis, a pair of litui were built from pine with the mouthpieces carved from cow horn. The bodies of both litui were made divisible into three separate pieces for portability reasons.
Brass Instrument Evolution Software
The Brass Instrument Evolution Software (BIES) provides an integrated software package which allows for the design, testing, and optimisation of brass instruments theoretically. One of its uses is that BIES makes it possible to obtain calculated input impedance curves for theoretically-described instruments. In addition, an optimisation routine forms one of its central functions whereby a target input impedance for an instrument can be specified and, should a suitable solution exist; an optimal input impedance curve and associated smooth instrument bore profile is produced. Throughout the optimisation process spherical-wave propagation is assumed.
One of the features of BIES is that it uses the Rosenbrock direct-search algorithm to find an optimised bore profile with the required input impedance curve across a more constrained design space. This has the effect of improving the convergence of the algorithm to a realistic instrument design and the time within which it does this.
So... how does the instrument sound?
Having built two litui in Basel, the instuments in concert sounded very similar to how it was originally thought they would sound. Sounding neither like a trumpet or an alphorn, but a sweetly-blended combination of the two. Needless to say, this sound worked well with the other instruments playing as part of the ensemble in both versions of Bach's cantata. In particular, the lituus appeared to work well with the sound and timbre of the singers.
Who was involved?
A team of scientists from the Musical Acoustics Laboratory in the School of Physics and Astronomy at the University of Edinburgh and musicians from the Schola Cantorum Basiliensis in Basel, Switzerland.
Reconstructing the Lituus: A Reassessment of Impedance, Harmonicity, and Playability.
A. G. Apostoli, S. M. Logie, A. Myers, J. A. Kemp, J. P. Chick, and A. C. P. Braden.
In proceedings of the NAG-DAGA International Conference on Acoustics; Rotterdam, The Netherlands (2009).
Trombone bore optimization based on input impedance targets.
A. C. P. Braden, M. J. Newton, and D. M. Campbell.
Journal of the Acoustical Society of America, Vol. 125(4), pp. 2404-2412, (2009)