8.6 Performing in a Hall: Blending Musical Performances with Sound Fields

upper valleys, both small sources of water. Then, as the piece develops, it becomes an expression of the joining of both streams into one and consists of increasing lowfrequency spectral component producing a wide image of the downstream flows into a broad valley.

Another example is Piano Sonata No. 14 in C sharp minor, Op. 27, No. 2 (“Moonlight”) by Ludwig van Beethoven, in which there are heavy low-frequency components (large WIACC) composed to represent an ambient vision of a big blue sky with a big body of water probably and spacious ground, while accompanying this with high-frequency components (small WIACC) representing a focused vision of the moon.

8.5.3Enveloping Music: Spatial Expression and Musical Dynamics

If the acoustic design for IACC in most of the seating area in a concert hall is small enough, then the strength of stage sound sources at volumes “ppp” to “fff” can be used to control subjective diffuseness as well as envelopment (Damaske, 1967/68). Musical dynamics and the resulting amplitude of reflections prevailing at the threshold level will decrease the perceived IACC, resulted in subjectively diffuse sound, while intentionally produced low dynamic levels can be used by the composer to produce a narrowing of the sound field environment.

8.6Performing in a Hall: Blending Musical Performances with Sound Fields

8.6.1 Choosing a Performing Position on the Stage

A performer can optimize the experienced quality of his or her musical performance by judiciously choosing where on the stage the music will be played. Soloists should select a position on the stage that yields an initial delay time of reflection, t1 that is most favorable to the music that they will perform. This in turn is mainly related to the range of the (τe)min value (Ando, 1998; Sato et al., 2000; Noson et al., 2002). The soloist may select a location on stage at the time of rehearsal, adopted both to ease of performance and thus to enhanced listener satisfaction. It is further recommended that a soloist situate near the middle or rear of the stage, rather than close to the front, in order to produce a small value of IACC most seating positions in the audience area.

The performing position that minimizes the IACC of the sound field for the listener’s seats is demonstrated here by means of an example. The values of IACC are calculated with music motif B [Arnold; (τe)min = 35 ms] at 112 listener positions in a Békésy Courtyard (Békésy, 1934). For simplicity, the directivity of the sound source is assumed to be uniform in this calculation. The height of the sound source

Fig. 8.31 Contour lines of equal averaged IACC calculated to find optimum performing position. The value was averaged for 112 listening positions. The most effective location of performance is found in the area IACC < 0.5

is 80 cm from the ground level, and the height of the listeners’ ears is 110 cm. The contour lines of equal average values of the IACC for 112 listener positions are calculated to find the optimum performing position and are then plotted in Fig. 8.31. The effective positions for performance may be found in the area minimizing IACC for all listening positions within the area of IACC < 0.5. A more effective procedure is that this positioning of a given concert space could be suggested by a “sound coordinator” of each concert hall (Section 8.6.3).

8.6.2 Performance Adjustments that Optimize Temporal Factors

Given a particular performing space, performers can adapt their playing style to match the acoustics of the space, and thereby enhance the perceived quality of the sound that they produce. One seeks to match the effective duration of the music performed with the reverberatory characteristics of the hall. Thus a pianist confronted with a smaller hall with short reverberation times can decrease the effective duration of the performed music by introducing staccato instead of legato, supper legato and full pedal (Taguti and Ando, 1997). One example is a performance by Glenn Gould, who performed by staccato, The Art of Fugue, Contrapunctus II & IX, that was composed by Johann Sebastian Bach (1685–1750). One can also control the minimum value of (τe)min in vocal performance, which determines the preferred temporal condition for vocal music. This strategy has been discussed as a means for blending the sound source and a given concert hall (Kato and Ando, 2002; Kato et al., 2004, Fujii et al., 2006, 2007). When vibrato is introduced during singing, for example, it can decrease the value of (τe)min, blending the sound field with a shorter reverberation time.

Because a characteristic of vibrato depends on the individual performer, the individual performer can be strongly urged to attain a skill for controlling the (τe)min value by use of a real-time ACF analyzer of music signals (Kato et al., 2006). In the

same manner, any performer may also play with a certain amount of vibrato or its equivalent for the particular instrument.

Conversely, if the reverberation time is long and the dimension of a given hall is large, then the (τe)min value should be controlled to be long. For example, the pianist can produce a long (τe)min value by legato, super legato, and full sustain pedal instead of staccato. And, the singer and the violinist can produce a long (τe)min value by decreasing the extent of vibrato.

Table 8.7 summarizes suggestive methods of controlling the (τe)min value of source signals.

In July 2004, the author requested Tsuyoshi Tsutsumi to present an invited special paper on blending cello music and the sound field in a concert hall. He immediately accepted this invitation and said that it is a “musical lifeline.” Tsutsumi (2006) has shown how cello music can be blended with the specific case of the sound field at the Kirishima International Music Hall. On the Internet, his musical performance is available at the Web site of the Journal of Temporal Design in Architecture and the Environment [Vol. 6, No. 3 (2006) 78–81; http://www.jtdweb.org/].

8.6.3Towards Future Integration of Composition, Performance and Hall Acoustics

The scientific approach made here suggests that further dimensions of musical temporal and spatial expressions in composition can be based on a concert hall’s acoustics (Table 8.8). In blending music sources performed on the stage with the temporal factor of the sound field in a given concert hall, we may take the effective duration of the ACF of the source signal into account, both for practical considerations (satisfaction of audience) and for artistic purposes (expressivity of the composer and performer). For spatial expressions, the strength of music source enhancing spatial sensations due to the perceived IACC and the frequency component due to WIACC could be carefully included in the production of each musical note.

After selecting a suitable performing position on the stage, music sources and the sound field in a concert hall may be fully blended by control of the temporal and the spatial expressions. For the temporal expression of the performer, methods of blending the temporal factor of the sound field have been proposed based on the effective duration of ACF of the sound sources. For spatial expression, the minimum source energy exceeding the threshold is needed to realize subjective diffuseness or envelopment for listeners.

It is hoped that the survey presented here might encourage musicians in furtherance of music composition and performance – using simultaneously the two primary instruments: the musical instrument and the given concert hall enclosure.

As a temporal design, if the conductor or music director is aware of the acoustics of a concert hall, they can plan a program of music that will sound best in that hall in terms of the temporal factors involved. This mainly depends on the minimum value of effective duration of the ACF of source signals, (τ e)min as discussed in Chapter 3.

178 8 Applications (I) – Music and Concert Hall Acoustics

It has been found, for example, that music with rapid sound movements or vibrato can decrease the value of (τ e)min, which best fits a concert hall with a short initial time delay gap t1, and a short subsequent reverberation time Tsub. Music with a slow tempo usually sounds best in a hall with relatively long values for the factor

t1 and Tsub.

An ideal application of this principle would allow the architect, concert hall manager, and music director to collaborate and actually change the configuration of a given concert hall to suit a specific music program. A “sound coordinator” could select a program of music that matches the acoustics of a given concert hall. Each major concert hall would have on hand such an expert in architectural and music acoustics, who could work with its music director to plan concert programs. The sound coordinator could suggest, for instance, appropriate music programs to be performed in the hall, optimal stage positions for performers, and possible modulations of the performing style. The professional role of this expert would be similar to the specialist of an art museum, with qualifications involving formal training at the professional school or college level in architectural and music acoustics. The existence of such positions would further new artistic creations that would utilize simultaneously the two primary instruments for the effective presentation of sounds: the musical instrument and the concert hall.

Beyond this, in order to realize truly excellent constructed environments, one should always explicitly consider both temporal and spatial values in the design process at its outset (Ando et al., 1996; Ando, 2004). A general theory of temporal and spatial design of environments has been proposed (Ando, 2009). Further development of temporal design ideas in architecture and the environment can be accessed in the Journal of Temporal Design (JTD, http://www.jtdweb.org/), which has been published since 2001.