title: Acoustic simulation of Bach's performing forces in the Thomaskirche
Creators: name: Boren, Braxton
name: Abraham, Daniel
name: Naressi, Rogerio
name: Grzyb, Elizabeth
name: Lane, Brandie
name: Merceruio, Daniel
Publisher: name: EAA Spatial Audio Signal Processing Symposium
Year: 2019
Subjects: Bach
Archaeoacoustics
Computational Musicology
Digital Humanities

description: Besides applications in gaming and virtual reality, acoustic simulation technology also has potential to transform historical musicology by rendering audible lost soundscapes from the past. This in turn may allow the role of historical spaces to be explored along with historical instruments and ensembles (Boren, Digital Scholarship in the Humanities, 2018). This requires individual recordings of each instrument being simulated, which involves many performers in the case of much of the Western classical repertoire. Simulation is also complicated by the fact that trained performers naturally alter their tempo and articulation in different acoustic environments (Fischinger et al., Psychomusicology 2015), but existing anechoic multi-instrument datasets have used a sync track to ensure that all musicians play at the same tempo, which removes the effect of the acoustic environment on the performer (Patynen et al., Acta Acustica United with Acustica 2008). This paper describes the project "Hearing Bach's Music as Bach Heard It," which addresses the acoustic sound field presented by the Thomaskirche in Leipzig, Germany in 1723, the start of J.S. Bach's tenure as cantor of the church. Musicologists disagree over whether Bach used a small or large chorus for his cantatas in the Thomaskirche and sometimes use acoustical arguments in favor of their preferred position (Jerold, The Musical Times 2017). The current project uses a combination of acoustic measurements in the current church and calibrated geometric acoustical (GA) modeling to simulate the acoustics of the church today and as it existed in 1723 and during the 16th century, using the method outlined in (Postma Katz, Virtual Reality 2015).Using this historical model, we have produced virtual sources for the primary groups of musicians Bach would have used, including strings (where Bach himself would have been located), woodwinds, continuo, trumpet, organ, and the choir. These sources have been placed in the GA model of the 1723 Thomaskirche's double galleries (which no longer exist) based on historical evidence of their locations during Bach's cantata performances. Each of these 6 sources was also used as a receiver, and the GA was used to generate binaural impulse responses for the 6x6 matrix of source-receiver combinations. In addition, three congregational source positions were simulated at different distances from the musicians along the nave of the church.The different binaural impulse responses are being used as real-time reverbs in ProTools during a recording session of a Bach cantata. This recording is planned for August 2019 with an entire ensemble in a dry room, with additional absorbing surfaces placed between sections, reducing but not eliminating bleed entirely. Using this setup, different musicological variables (i.e. one voice per choral part or four voices per part) and acoustical variables (i.e. the BRIR from 1723 or from the present day) can be tested during multiple recordings of the same chorale. This method allows the final auralization to incorporate the effect of the church's acoustics on the performance as well as the response at the audience's position. Further discussion is needed for an optimal method for recording large ensembles dependent on the latency and bleed present in different setups, as well as the infrastructure needed to simultaneously record multiple performers in multiple rooms.