Proceedings of the Institute of Acoustics

MUSIC AND ARCHITECTURE THROUGH THE AGES C Diaz Brito Engineer, Buro Happold, London, UK B F Burgess Director, Buro Happold, London, UK D Prasad Associate Director, Buro Happold, London, UK 1 INTRODUCTION

The perfect acoustic conditions in which to perform a Bach sonata are naturally very different from the ideal acoustic conditions to perform a Shostakovich symphony. The difference in the acoustical demands of these musical pieces lies in the different stylistic music features, which encompass a range of factors including instruments used, size of the ensemble, melody structure, music texture and dynamic scope, among others. This paper analyses the relationship between musical and architectural styles throughout history and considers the ideal acoustical demands for each genre. The aim is to understand the room acoustic conditions best suited for different music styles and how they have been accommodated in the past. This can then be extrapolated to contemporary concert halls to strike a balance between commercial and artistic needs for a successful venue. 2 THE LANGUAGE OF MUSICAL ACOUSTICS

2.1 Introduction

Music is a language in itself. It is a form of expression, of communication. It has emotional power, it has nuances, and it naturally entails a particular jargon. One of the branches of this jargon revolves around the attributes of the spaces in which music is performed, in terms of the room’s effect on the sound generated by performers. Musical acoustics has emerged as a result of the dialogue between musicians and acousticians. Speaking the niche language of musical acoustics is the foundation for successful collaboration between musicians and designers. There are a number of popular musical acoustics terms which are used to describe subjective, psychoacoustic perceptions 1,2 . Scientists and engineers have made best efforts to define objective and measurable parameters 3,4 , which can be used to design venues. Three subjective terms have been selected for the purposes of this study and their relationship with objective parameters (defining the varying ideal acoustic conditions for different musical genres) has been investigated. 2.1.1 Fullness of tone

The term “fullness of tone” is related to reverberation, which is the prolongation of a sound in a space until it is ultimately attenuated, principally due to air absorption and room finishes. A long reverberation time often results in the sound being perceived as “full”. Fullness of tone can be thought of as the bridge between gaps in discrete sounds. This commonly used term can be associated with parameters such as Reverberation Time ( T 60 , T 30 , T 20 ) and Early Decay Time ( EDT ).

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Proceedings of the Institute of Acoustics

2.1.2 Clarity

This term represents the musical acoustics concept, which can be thought of as the opposite of “fullness of tone”. Clarity can be described as the ability of a space to transfer information from a source to a listener with minimal loss of data. While a long reverberation time may blur the definition between musical notes, a shorter reverberation time can lead to higher clarity by providing space in which each note can be distinct. Clarity can be associated with the quantifiable parameter Musical Clarity ( C 80 ). It is important to note the subscript, which refers to the time period in which the direct sound and early reflections energy is evaluated. In building acoustic design for non-musical spaces, 50 ms is often employed to assess the clarity of speech, with reflections arriving at the ear later than this generally accepted to reduce speech clarity. For musical sounds however, the time period in which both the direct sound and useful early reflections can arrive is considered to be 80 ms. 2.1.3 Spaciousness

Whilst fullness of tone and clarity may be naturally evident ideas, spaciousness is a more subjectively abstract concept. It refers to the sense of a sound source being perceived as physically wider than in physical reality. The term can be associated with different perceptions of sound such as the overall feeling of loudness, spatial impression, quality and quantity of timbre, or distance to sound source. Due to its link with various perceptions, there are a number of quantifiable parameters with which it can be associated, such as Sound Strength ( G ), Initial Time Delay Gap ( ITDG ) and Lateral Fraction ( LF ). 3 BAROQUE ERA

3.1 Baroque music

The Baroque era in most forms of art is defined by dramatic effects, flamboyant ornaments and a strong sense of movement. This is reflected in the music through vibrant rhythms and dramatic contrast in dynamics – abrupt shifts from loud to soft. The decorative aspect is present in the use of intertwined melodic lines, which “embroider” a complex texture. The Baroque orchestra was relatively small, with 10 to 30 players, primarily strings. Most of the classical instruments that are known today existed in the Baroque era, though in some cases in a less developed form. One particularly relevant aspect of the Baroque instruments is that they are not able to project sound as efficiently and intensely as their more contemporary counterparts. 3.2 Baroque concert halls

Secular music in the Baroque era was associated with court surroundings. It was performed mainly as a form of aristocratic entertainment in palace courts and chambers. These private spaces were typically rectangular rooms with hard (acoustically reflective) floors, ceilings and walls. Compared to modern concert halls, they were relatively small, leading to low reverberation times. Additionally, elaborate ornaments and decorations were a common feature in walls and ceilings, adding significant scattering to these surfaces.

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Proceedings of the Institute of Acoustics

3.3 Baroque acoustic demands

The highly articulated and rhythmical nature of Baroque music requires sound to be sufficiently clear. High clarity and low fullness of tone are critical to provide a good listening experience for Baroque music and enabling its stylistic features to flourish. This is of particular relevance with respect to the complex textures, which require the various melodic lines to be intelligible and clear. The architectural features of the palace courts provided perfect conditions for the acoustical demands of the music, although it could be argued that the relationship actually developed in reverse. In this sense, the music style developed in such a way due to being performed in palace chambers. The relatively small volume of the spaces enabled sound to feel intimate and provided a controlled reverberation time. The rectangular room geometry plays a crucial role in providing spatial and dynamic responsiveness, which naturally leads to highly expressive music with noticeable contrasts. Furthermore, the highly embellished nature of the walls and ceilings promotes a sense of envelopment due to sound reflecting off ornaments in different directions, leading to a diffused sound environment in the space which surrounds listeners. The acoustical demands of Baroque music have been assessed based on its stylistic features and have been summarised in Table 1. Modern venues intended to accommodate Baroque music should aim to provide these acoustic conditions so that music can be performed as it was originally intended and so that period instruments can suitably project sound to the audience. Some outline architectural features that can facilitate these conditions are listed below.

 Relatively small room volume  Short distance from the listener to the stage  Stage support if room volume is large  Nearby surfaces to reflect early sound energy to the audience. In shoebox halls, the first sound reflections are typically provided by the side walls or balcony fronts. In wider halls, suspended panels or ceiling elements are relied upon to provide early reflections.  Where the room volume is large, the reverberation time should be lowered through the strategic location of sound absorption Table 1 Acoustical demands of Baroque music

Subjective parameter Objective parameter Magnitude Fullness of tone T 60 Very low Clarity C 80 Very high

ITDG Very low G Very high LF High 4 CLASSICAL ERA

Spaciousness

4.1 Classical music

In the Classical era, the focus shifted towards symmetry and proportion. The musical texture became mostly homophonic, with short melody lines predominating over an accompaniment. The use of dynamics was expanded through gradual changes in loudness, rather than abrupt changes. This was enabled through the development of existing instruments, which were capable of producing new timbres and generating higher sound levels, and the increasing size of the orchestra, with 30 to 60 players organised into four sections – strings, woodwind, brass and percussion.

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Proceedings of the Institute of Acoustics

4.2 Classical concert halls

With the concept of popular concerts being established, concert halls were open to the public during the Classical period. These halls were larger spaces that could accommodate an audience but, architecturally, they still generally consisted of rectangular halls with a flat ceiling. 4.3 Classical acoustic demands

The shift towards a more unified musical texture meant that clarity of sound was not as critical as it was during the Baroque era. This, coupled with the increased dynamic scope of the orchestra, led to a demand for more fullness of tone. The larger sizes of the halls meant that the sound of the orchestra was inherently perceived as more full and rich. However, musical sounds still benefited from clarity due to the strong early reflections provided by the narrow walls. Table 2 provides a summary of the assessed acoustical demands of Classical music, based on the described stylistic features. Contemporary venues designed to cater for Classical repertoire should enable these acoustic conditions in order to see that the music can be interpreted as originally written. Some outline architectural features that can facilitate these conditions are listed below.

 Medium room volume  Nearby surfaces to reflect early sound energy to the audience proportional to the room volume (heavy localised concentration early energy may result in areas of the hall being perceived as too loud)  Strong lateral sound reflections  Limited sound absorption in the hall Table 2 Acoustical demands of Classical music

Subjective parameter Objective parameter Magnitude Fullness of tone T 60 Low Clarity C 80 High

ITDG Low G High LF Very high 5 ROMANTIC ERA

Spaciousness

5.1 Romantic music

It was during the Romantic period that music became more connected to other forms of art, and grew passionate and intensely expressive. Stylistic trends include long, lyrical melodies with a great variety of tone colours, orchestral effects and rich textures. Composers of the era broke with the rigid rules of Classicism and stretched the size and dynamic scope of the orchestra. Improvements and optimisations were made to existing instruments with updated valves, keys and hammers, which enabled extreme dynamics to be explored. Orchestra sizes increased significantly, incorporating up to 100 or more.

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Proceedings of the Institute of Acoustics

5.2 Romantic concert halls

The Romantic era saw the development of many great concert halls around the world. The size of the concert halls gradually increased in order to accommodate larger audiences. However, the geometry of the halls still showed the influence of historical “shoebox” venues but started to divert from the simple rectangular shape. 5.3 Romantic acoustic demands

Whilst in Baroque and Classical music discrete sounds needed to be clear and intelligible, for Romantic music the aim is to perceive a blend of all musical sounds and effects from the orchestra. The acoustical desire was for high fullness of tone and low clarity of sound. New acoustic features such as warmth and spaciousness started to play a crucial role in the listening experience. The acoustical demands of the music were supported by the large volumes of the halls, which provided longer reverberation times. The long distance from the audience to the stage and the nearby reflecting surfaces lead to much lower clarity of sound and intimacy, which were perfectly suited for the music style. The grandiose sounds of the Romantic repertoire require radically different acoustic conditions to those of the previous periods. In order to promote the intended expressiveness of this music style, the acoustical demands listed in Table 3 should be provided in halls. These conditions may be achieved by implementing the following example architectural features:

 Large room volume  Nearby surfaces to reflect early sound energy to the audience proportional to room volume  Very strong lateral sound reflections  Use of thick, heavy materials to form the ceiling/soffits and walls and limited upholstery to limit low frequency sound absorption. This will provide “warmth” to the sound by enabling low frequencies to sound stronger. Table 3 Acoustical demands of Romantic music

Subjective parameter Objective parameter Magnitude Fullness of tone T 60 Very high Clarity C 80 Low

ITDG Medium G Medium LF Very high 6 MODERN/POST-MODERN ERA

Spaciousness

6.1 Modern/Post-modern music

Modern and Post-modern music reflects the artistic movement towards innovative, abstract ideas. Composers became very inventive and explored undiscovered ways of expressing music, which included the development of a new tonal system Dissonances and complex rhythms were the new norm and were emphasized through extreme dynamics and expressiveness. However, orchestra sizes reduced slightly from the Romantic period to an approximate limit of 100 players.

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Proceedings of the Institute of Acoustics

6.2 Modern/Post-modern concert halls

The ambition to host large audiences took over in the 20 th century, pushing designers to experiment with new, less-established concert hall shapes. It was during this experimental period that poor sound became more apparent as concert halls diverted more and more from the ballroom proportions. The “vineyard” shape was invented, incorporating surround seating, a tent-like ceiling, and cascading balconies. Other new experimental settings such as fan-shaped halls were explored. Some of these new styles led to very impressive architectural effects. However, this sometimes resulted in an underwhelming listening experience. 6.3 Modern/Post-modern acoustic demands

Due to the broad span of musical sounds that Modern and Post-modern compositions offer, contemporary halls need to strike a balance between the different possible acoustical conditions. This is further emphasised by the challenge of accommodating earlier music styles, which divert considerably in acoustical demands. A current trend is to provide intimate sound experiences, whilst allowing musical sounds to be rich and envelop the listener. This may be achieved by adopting the acoustic conditions described in Table 4 below. Some architectural features that can be incorporated to promote these conditions are listed below:

 Large room volume with an adjustable reverberation time  Nearby surfaces to reflect early sound energy to the audience in accordance with room volume  Stage support to promote sound strength  Very strong lateral reflections where possible  Uniformity of sound in the audience area  Balance the sound absorption at low and high frequencies through dense materials. Table 4 Acoustical demands of Modern/Post-modern music

Subjective parameter Objective parameter Magnitude Fullness of tone T 60 Very high with the capability to adjust it Clarity C 80 Medium

ITDG Medium G Medium LF Very high

Spaciousness

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Proceedings of the Institute of Acoustics

7 NON-CLASSICAL MUSIC

Contemporary concert halls often host non-classical concerts. The sounds generated during amplified music concerts (such as Pop or Rock) are radically different to the unamplified orchestral sounds. Higher sound levels with a much smaller dynamic range are usually the norm for amplified music. A key difference is the low frequency content. Bass guitars and bass drums contribute to the large amount of sound energy at the low frequencies. This type of music demands a balanced reverberation, particularly at low frequencies. This is to prevent sound from becoming “muddy” or “boomy”, and potentially masking other musical sounds, particularly song vocals. Measures that can be put in place to cater for this type of music include the addition of low frequency absorption (especially at 63-125 Hz) 5 and the limitation of high frequency absorption (which is inherently provided by the audience). 8 REFERENCES

1. L. L. Beranek. Concert Halls and Opera Houses Music, Acoustics, and Architecture. 2 nd ed Springer (2004) 2. T. Lokki, J. Patynen, A. Kuusinen, S. Tervo. Disentangling preference ratings of concert hall acoustics using subjective sensory profiles. J. Acoust. Soc. Am. 135 (5). (2012) 3. J. R Hyde. Discussion of the Relation between Initial Time Delay Gap (ITDG) and Acoustical Intimacy: Leo Beranek’s Final Thoughts on the Subject, Documented.(2019) 4. D. H Griesinger. What is “clarity”, and how it can be measured? Proc. Mtgs. Acoustic. 19 5. N. W. Adelman-Larsen, E. R. Thompson and A. C. Gade. Acoustics in rock and pop music halls. Audio Eng. Soc. Convention Paper, 122 nd Convention. Vienna (2007)

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