Timbre Research Articles

The application of the Alexander Technique to flute teaching: two case studies

Two case studies of different ages, levels of progress, capabilities and backgrounds are investigated in the light of methods employed by F. M. Alexander for inculcating relaxation in actors and musicians (the so-called ‘Alexander Technique’). The various tensions in the two learners, both physical and mental, were identified, the reasons therefor sought, then solutions provided and effected. The process is described in some detail and the development, most specifically regarding the improvement in tone quality, traced through its various stages. Specific Alexander techniques are described, with their in situ applications documented. The positive effects of correct posture are thereby demonstrated.

The acoustics of the bawu

The bawu employs a metal free-reed mounted in a bamboo resonating pipe with several finger holes. It is closely related in principle of operation to other Asian free-reed instruments, including the sheng of China, the sho of Japan, and the khaen of Thailand and Laos. In these instruments the reed vibration is strongly coupled to the pipe resonance, which is typically close to the natural frequency of the reed. The bawu, in contrast, employs a pipe resonator of variable effective length (using the tone holes) in which the pipe resonance and sounding frequency are both above the natural reed frequency. The most striking result of this is a significant change in tone quality. Variations in frequency and sound spectrum with blowing pressure have been studied, and some aspects of reed design and construction have been investigated. The relationship between frequency of reed vibration and pipe length has been studied to determine the range of pipe length over which the reed can be made to sound, as well as the amount of frequency shift associated with changes in resonance frequency of the pipe.

The Effects of Live Accompaniment, Intelligent Digital Accompaniment, and No Accompaniment on Musicians' Performance Quality

This study is an investigation of differences in performance-quality ratings among college-age instrumentalists grouped in three solo preparation conditions using (a) no accompaniment, (b) live accompaniment, or (c) intelligent digital accompaniment. After a 6-week practice period, participants performed an intermediate level solo on a secondary wind instrument in two conditions: (1) without accompaniment, and (2) within prescribed accompaniment mode. Data from the first (unaccompanied) and second (assigned accompaniment mode) performance ratings were compared. Highest ratings across all groups in both performances were achieved in Rhythm, Technique, and Articulation. Lowest ratings were shown in Intonation, Tone Quality, and Interpretation. The second performance ratings declined in the Accompaniment groups but rose for the No Accompaniment group. Groups demonstrated different performance outcomes in each of six category ratings with Rhythm being the highest rated category among all groups. Different effects of practice and performance circumstances on musical outcomes were demonstrated.

Dislocation Substructure Contributions to the Tonal Qualities of the Caribbean Steel Drum - A TEM Study

Deformation substructures, especially dislocations, play an important role in the fabrication of the Caribbean steel drum and experimental evidence also suggests dislocations play a crucial role in the harmonic tuning and related musical qualities as well. In this study, we have examined and compared the dislocation substructures in high-quality, low-carbon (0.04-0.06 weight percent carbon) steel drum heads as manufactured, and sections cut from variously deformed (10% to 50% reduction) drum head sections, including those patterned with musical notes and heat treated; utilizing TEM.We have recently shown that the requisite heating of a steel drum over a narrow temperature range (200 to 500°C) prior to tuning actually involves strain aging. Fundamentally, strain aging in steels has been explained by dislocation theory, but as far as we know, no experimental proof exists. This study also attempts to examine the more fundamental issues in strain aging, especially as it applies in the development of a high-quality, musical steel drum instrument.

Acoustic properties of a reed (Arundo donax L.) used for the vibrating plate of a clarinet

The effect of water-soluble extractives on the acoustic properties of a reed (Arundo donax L.) used for the vibrating plate of a clarinet was investigated at various relative humidities (RH). At low RH levels, the extractives enhanced the dynamic Young’s modulus of the reed. This effect was reduced with increasing RH because of the deliquescence of extractives. It was suggested that the quality of the reed is improved by the extractives reinforcing its dry part. The extractives also increase the density and the internal friction of the reed remarkably. These might affect the frequency response of the reed to make the tone richer and softer. The tone quality of the reed lost by the removal of extractives was reproduced by impregnating the reed with glucose, which is the most abundant constituent of natural extractives.

Effects of Tone-Quality Changes on Intonation and Tone-Quality Ratings of High School and College Instrumentalists

We investigated the effects of variations in tone quality on listeners' perception of both tone quality and intonation. University music and nonmusic major instrumentalists and high school students participating in instrumental ensembles served as listeners ( N = 116). High-quality digital samples of clarinet, trumpet, and trombone tones were used. The original tone quality of each instrument was manipulated to produce experimental stimuli of “bright” and “dark” relative to the unaltered tone quality. Results indicated that the more inexperienced instrumentalists rated stimuli that were relatively “brighter' in tone quality as sharper in intonation, and conversely, stimuli of relatively ”darker' tone quality were judged to be flatter in intonation. For the brass instruments, listeners judged the unaltered and bright tones as better in tone quality than tones that were relatively dark. However, for the clarinet tones, the bright tone quality was judged to be worse than unaltered or dark-quality stimuli.

Aural-Diagnostic and Prescriptive Skills of Preservice and Expert Instrumental Music Teachers

This study is an investigation of the aural-diagnostic and prescriptive skills of preservice and expert instrumental music teachers. Specifically, the researcher sought to determine how the two groups compared with respect to evaluations for band performances of different music-difficulty and performance-quality levels. Subjects listened to an audiotape recording that comprised four types of performances: Difficult Music and Excellent Performance, Difficult Music and Average Performance, Moderate Music and Excellent Performance, and Moderate Music and Average Performance. For each performance type, subjects responded to four evaluative areas in the investigator-designed Aural-Diagnostic and Prescriptive Skills Test: performance-quality ratings of nine select music elements, rankings of the nine elements, diagnoses of performance problems associated with the weakest-ranked elements, and prescriptions of rehearsal solutions for the diagnosed performance problems. Results indicate that (a) regardless of performance types, preservice teachers rated Intonation lower than did expert teachers; (b) interactions exist among the four performance types for subjects' ratings of Tone Quality, Intonation, Articulation, and Dynamics; and (c) compared to preservice teachers, a higher proportion of expert teachers ranked Blend/Balance and Musical Interpretation as the weakest- performed music elements.

Tone quality and important modal properties of the guitar

The main function of a string instrument’s body is to convert string vibrations into radiated sound that is detected by the listener. The coupling between string and body modes determines the vibrational response of the instrument to a plucking/bowing force applied to the string, and therefore has a crucial influence on the instrument’s sound. The nature of this coupling depends on the body’s modal properties as detected at the bridge. An interesting question arises: how do changes to the body modes affect the perceived tone quality of the instrument? The use of numerical models permits independent control of an instrument’s modal properties. By performing psychoacoustical tests with sounds synthesized from these models one can examine the effect on perceived tone of changes to individual body modes. In relation to the guitar, this approach has shown that mode shapes, and, in particular, the positions of nodal lines in relation to the bridge, have a powerful influence on tone quality. This paper reviews the current understanding of the links between the guitar’s modal properties and its sound, and highlights the need for further numerical and psychoacoustical work as a means of extending our knowledge in this area.

Psychoacoustic model for calculating the sound quality of piano tones

Assuming that only audible dissimilarities between different piano tones may lead to different quality judgments, experiments were conducted to determine the perceptual attributes listeners use to judge these dissimilarities. The psychoacoustic results showed that two major attributes contribute with over 90% to the explanation of the perceived dissimilarities: the psychoacoustic ‘‘sharpness’’ and a second attribute that was described with the scale ‘‘open–closed.’’ Both attributes depend on the specific loudness distribution of the sound signals and are defined as a weighted first moment of the critical-band rate distribution of specific loudness using different weighting functions. The weighting function used to calculate the second attribute emphasizes spectral components around 1 kHz. The model developed for calculating audible dissimilarities between piano tones showed a good agreement between psychoacoustically measured and calculated dissimilarities; the correlation was 0.90. The influence of the two attributes on sound quality judgments was verified by listening tests with appropriately modified piano sounds. The results showed that calculating the sound quality of musical instruments on the basis of their sound signals requires an aurally adequate signal processing. The model developed to calculate the sound quality of piano tones showed a good agreement between measured and calculated quality orders.

Sound quality design for high-speed trains’ indoor noise: Psychoacoustic evaluation of tonal components

For the specification of the sound quality inside future high-speed trains, tonal components produced by the motors or corrugated rails can play an important role. Therefore, in psychoacoustic experiments, the dominance of tonal components at 630 or 1250 Hz was assessed. For an increase of the corresponding 1/3-oct band by 20 dB, a clear tonal character is audible which is only half as pronounced for an increase of 12.5 dB at 630 Hz or 10 dB at 1250 Hz. In line with the expectation, no tonal quality is perceived, if the 1/3-oct band in question is not enhanced. However, a decrease of sound energy in a 1/3-oct band by 20 dB can also produce a faint tonal sensation with a magnitude of about 1/10 of the tonal sensation produced by an increase of 20 dB. The results obtained with stimuli simulating the sound quality inside high-speed trains are in good agreement with data from basic psychoacoustic experiments. Therefore, it is expected that sound quality evaluation of high-speed trains indoor noise can profit from a multitude of psychoacoustic data available.

Quality aspects of violin bows

The string player’s test of a bow includes four major aspects: (1) the bow should be ‘‘well balanced’’ with an appropriate total weight; (2) the bow should have a good grip of the string over the entire length of the bow stroke; (3) the ‘‘timbre of the bow’’ should be pleasing; and (4) the bow should bounce easily in advanced bowing patterns like rapid spiccato and ricochet. A poor bow will: fatigue the player by demanding too much physical effort (in particular in string crossings); tend to lose the grip of the string when approaching the tip; disguise the tonal quality of a fine instrument; and be sluggish and scratchy in rapid bouncing sequences. Some plausible physical properties which govern these four quality aspects will be presented, focusing on the last, the bouncing bow. [Work supported by School of Electrical Engineering, Royal Institute of Technology, Stockholm.]

On the effect of phase relations for the perception of pitch and timbre of bass tones

In contrast to the old classic statement that the human ear is insensitive to phase relations, many results have been published by psychoacousticians that demonstrate the influence of phase on timbre and pitch perception in experimental situations. The experiments usually involve artificial complex tones consisting of high order (unresolvable) harmonics restricted to a specific region of fundamental frequencies. A musically important question is whether or not the effects of phase on pitch and timbre perception are sufficiently strong to be relevant to discussions of the tone quality of real musical instruments. Acoustical analyses and tests of perception in the bass range, where temporal processes are thought to be prominent, provide promising means of studying such effects. Experiments with phase relations in bass tones will be presented. The examples range from harmonic steady multicomponent tones with flat spectrum to inharmonic tones with pianolike spectral dynamics. The results presented have implications for psychoacoustical demonstrations and for a batter understanding of the tone quality of musical instruments, in particular the piano.

多重マップモデルによる２種の情報の分離抽出

Self-organizing continuously-overlapping map is shown to have ability to detect the first and second nonlinear principal components. This is an extended version of the self-organizing overlapping mapping. The model was applied to FFT data of sound, and some others. These data are characterized by a combination of two kinds of features, such as the pitch and the quality of tone. The model has two self-organizing layers. One layer extracts and maps continuously one feature, and the other layer does the same with respect to the other feature. The ability of generalization depending on data structure is demonstrated. Comparison to Kohonen's SOM is also discussed.

Bandwidth of perceived inharmonicity for physical modeling of dispersive strings

The influence of accurate reproduction of inharmonicity on the perceived quality of piano tones is investigated. Acoustic piano tones were resynthesized by changing the bandwidth of correct positioning of partials. Cutoff frequencies of inharmonicity for different pitches have been established by psychoacoustic experimentation. The results are applicable to the design of dispersive resonators in sound synthesis by physical modeling.

Musicians' Ratings of Good versus Bad Vocal and String Performances

This study continues a line of research attempting to ascertain the focus of musicians' attention when listening to music. It is the fifth study in a series structured to determine whether musicians demonstrate consistent listening patterns across excerpts intentionally designed to be perceived as good and bad performances. Soprano, tenor, violin, and cello excerpts varied considerably in intonation and tone quality and, to a lesser extent, in other performance aspects. In this study, 48 music students were asked to rate excerpts on traditional performance evaluation rating scales (phrasing/expression, intonation, rhythm, dynamics, tone quality) and give an overall rating. Results indicated that musician listeners consistently discriminated between the good and bad performances across all rating scales. Intonation was identified as the element most in need of improvement in performances. Significant differences were found also between the four timbres and the accompaniment conditions. Results of acoustical analyses that portray a variety of differences in the performances are discussed in relation to listener ratings.

The colour of music: Spectral characterisation of musical sounds filtered by a cochlear model

In music research, attention is more and more focused on the main factors of sound perception: This holds in particular for the capability of discriminating music sound features, notably attacks and periodic components, both of which are believed to generate timbre sensation. In this paper it is argued that the frequency spectrum of the stationary part of instrument sounds are coded, at some stage, within the nervous system, into a small number of parameters. Somewhat as in vision the light spectrum of a uniformly painted area is coded by the retina into three fundamental colours, the sound parameters seem to represent what may be called “instrument sound colours”. The analysis is carried out on music sound samples pre‐filtered by a non‐linear model of the human cochlea. The main reason for this approach lies in the fact that the non‐linear filtering performed by the cochlea works to reduce significantly the‐information content of acoustic input. Some properties of the model, particularly those related to the efficacy of non‐linearity in tone masking and noise suppression, are evidenced by examples. The reliability of the model in sound colour characterisation, also in the case of noise‐added sounds, is investigated as well. A principal‐component analysis of cochlear responses to sounds generated by 21 musical instruments seems to indicate that the spectra of the stationary parts of instrument sounds are perceived as combinations of three fundamental components.

Syllable-beat-point synchronized rule-based speech synthesis from coded utterance-speed-independent phoneme combination parameters

In a speech synthesizer, each frame for generating a speech waveform has an expansion degree to which the frame is expanded or compressed in accordance with the production speed of synthetic speech. In accordance with the set speech production speed, the time interval between beat synchronization points is determined on the basis of the speed of the speech to be produced, and the time length of each frame present between the beat synchronization points is determined on the basis of the expansion degree of the frame. Parameters for producing a speech waveform in each frame are properly generated by the time length determined for the frame. In the speech synthesizer for outputting a speech signal by coupling phonemes constituted by one or a plurality of frames having phoneme vowel-consonant combination parameters (VcV, cV, or V) of the speech waveform, the number of frames can be held constant regardless of a change in the speech production speed. This prevents degradation in the tone quality or a variation in the processing quantity resulting from a change in the speech production speed.

Influence of the weight of mutes on tones of a violin family

The phrase ‘‘con sordino’’ is used for the score of a violin family to indicate the use of a mute. The mute is used to reduce the volume of the violin tones and change their tone quality. This paper examines the influence of the weight of mutes on tones of a violin using the spectral envelopes of the violin tones. Violins with and without mutes were played by a skilled player in an anechoic chamber to produce tone samples which were then recorded on a DAT recorder. Using the tone samples, the time variances of the fundamentals and spectral envelopes obtained by FFT analyses were examined. The force transfer function of a cello bridge with mutes installed, which is used for convenience, was measured. From these examinations and analyses, we made the following observations: (1) the higher the order of harmonics, the lower their relative sound pressure levels compared with that of the fundamental and (2) the level differences between the peaks and dips of the spectral envelopes are reduced as the weight of a mute is increased.

Dynamic mechanical measurements on violin wood and audience evaluations of violin tone quality

At the 125th Acoustical Society of America meeting in Ottawa, Canada, values of complex shear compliance (J*=J′−iJ″), modulus (G*=1/J*), and shear wave velocity and attenuation, measured over a continuous frequency range from 10 to 10 000 Hz at 20 °C and 50% RH, were described for samples of spruce and maple wood used in the construction of six violins. Four wood samples were measured for each violin, viz., samples of spruce and maple with and without cross grain. Relation of the violin wood dynamic mechanical properties to plate tuning of the violins also was discussed. Following these presentations, two members of the Ottawa Symphony orchestra each played two short pieces on each of the six violins, and the audience was asked for written comments on the tone quality of each violin. The evaluations display some variations as to the violin(s) with the best tone, but one of the six was rated as good or best tone by none, and the worst tone by many. The dynamic mechanical shear properties of this violin’s wood differ in several respects from those of the other violins. Similar property differences for this wood relative to the others also exist in extensional moduli determined from flexural vibrations.

THE STEELPAN AS A SYSTEM OF NON-LINEAR MODE-LOCALIZED OSCILLATORS, PART III: THE INVERSE PROBLEM—PARAMETER ESTIMATION

This paper is the third in the series on this topic. In the earlier papers, the dynamics of the steelpan notes were developed as systems of non-linear mode-localized oscillators which can show note–note and note–skirt coupling. The tonal qualities of a note depend on the coupling parameters and damping coefficients. Here, the inverse problem of parameter estimation is presented for notes that do not show coupling to other subsystems of the instrument.