VITA 2010

  Vienna Talk 2010 on Music Acoustics
"Bridging the Gaps"
      September 19–21


Stringed instruments (E. Schoonderwaldt)

This session will be on stringed instrument acoustics. Papers on bowed instruments, plucked stringed instruments, piano, harp etc. will be accepted

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Demoucron; Matthias: 
(Invited) / O
In violin playing, the properties of the sound are shaped continuously through the control of three main bowing parameters that are the bow force, the bow velocity, and the bow-bridge distance. The mastering of the range and the time evolution of these bowing parameters in different playing situations is one of the main challenges of the violinist's education and training. Furthermore, playing violin also requires the mastering of different bowing techniques like staccato, or spiccato, which are very dynamical and short bow strokes.
Technologies like motion capture and sensors allow measuring the effective bowing parameters used by the performer in real performances. These measurements can be analysed in order to characterize playing techniques and differences among musicians. In this paper, we will present measurements of control parameters for basic classes of bowing patterns (sautillé, spiccato, martelé, tremolo), whose performance is mainly based on reproduction of well-practiced motor behaviour, more than on conscious control in real-time. Because a proper performance of these bow strokes requires extensive practicing under a long period of time, they exhibit characteristic and reproducible bowing parameter patterns. The time evolution of the bowing parameters was modelled by analytical functions, which allowed to describe and characterize bow strokes by a limited set of control parameters.
Grosshauser; Tobias: 
(Invited) / O
Motion and gesture are important parameters in musical instrument playing and examined extensively in many studies and research projects. But additionally pressure and force are important parameters, but still very little research is done in this area. Pressure sensing technologies allow to measure and interpret complex and hidden forces, which appear during playing a musical instrument. The combination of our new sensor setups with pattern recognition techniques like the lately developed ordered means models allows fast and precise recognition of highly skilled playing techniques. This includes left and right hand analysis as well as a combination of both. In this talk we show bow position recognition for string instruments by means of support vector regression machines on the right hand finger pressure, as well as bowing recognition and inaccurate playing detection with ordered means models adapted to individual students. We also show a new left hand and shoulder/chin sensing method for coordination and position change analysis. Our methods in combination with our audio, video, and gesture recording software can be used for teaching and exercising. Especially studies of complex movements and finger force distribution changes can benefit from such an approach. Beside the sensing part of also the feedback part is examined. Beside visual feedback, audio and haptic feedback methods are tested and evaluated. Additional audio as well as haptic feedback closes the loop from sensor signals over data manipulation to the user in realtime and postprocessing scenarios. In general, all data allow precise off-line examination and comparision for advanced gesture and motion studies. Practical applications include the recognition of inaccuracy, cramping, or malposition, and, last but not least, the development of augmented instruments and new possibilities for modern music.
Guettler; Knut: 
(Invited) / O
To our knowledge the book “Motion Study and Violin Bowing” by Percival Hodgson, published by Lavender in London 1934 (and reprinted by American String Teachers Association in 1958), was the first attempt to describe the acoustical consequences of bowing gestures. At least, if reserving the term “bowing gesture” for dynamic bow movements. The study was aimed at string players, and was based on an ingenious method for recording the bow’s motion during performance. Later the utilization of many novel techniques, including robotics, numerical simulation, and digitalized optical motion capture has greatly contributed to increased understanding of how the bow-string contact actually works, even on a rather detailed level. This presentation walks through a number of different projects and methods, and discusses the results and their usage as seen by the performer, the string teacher, and the acoustic researcher.
Schoonderwaldt; Erwin: 
(Invited) / O
Detailed measurements of bow motion in the performance of musical pieces can give new insights in subtle aspects of control in tone production by string players. I will present detailed analyses of arpeggio passages across two and three strings in several performances of the Preludium of the third Partita for solo violin by J.S. Bach. The bowing patterns are characterized by a quasi-periodic motion of the bow, which can be visualized as Lissajous curves. The two movement components corresponding to bowing the string and string transitions show an interesting phase relation, where the string crossings slightly lead changes in bowing direction. An acoustical explanation for this behavior is that it results in clear attacks, and this can therefore be considered as a good example of optimization in human sensorimotor learning. A comparison will be made between performances by two advanced players, one of them familiar with the piece, and the other one sight reading it, as well as a performance by an amateur player.
Taylor; Crissman: 
(Invited) / O
A research and education project at Utrecht Conservatory helped violin and viola students overcome chronic tension and cramped playing. Research charted the link between ill-fitting chin and shoulder rests and recurrent difficulties in technique. Chosen or constructed chin and shoulder rests helped to eliminate cramped playing habits. In weekly group meetings students overcame fear of losing control of their playing technique, releasing them to try something new. Weekly private Alexander Technique lessons proved essential in helping students to overcome old habits and accustom themselves to improved equipment.
Typically violinists and violists are attached to their cramped style of playing and are unaware of other options. Initially students believed that pulling their head down and enduring overall muscle tension was necessary for expressivity.
We discovered that ill-fitting equipment was common, causing physical and technical stress. Re-alignment of the instrument brought ease and facility to bowing and fingering. Placement of the instrument on the collar bone increased sound through bone resonance. Adjusted chin rest and shoulder rest combined with re-training of cramped playing technique improved coordination and eliminating playing-related pain and discomfort. As they came out of cramped playing positions, students also reported being able to “see and hear better,” and reduction of sensory background noise allowed them to feel themselves and their instruments better.
At year’s end, many students found playing techniques that formerly eluded mastery came within reach or simply “solved themselves.” One student summed it up: “Probably the most important thing that I got from all this was that I was not the problem. I only needed to find the way to solve the problem.”
van der Linden; Janet: 
(Invited) / O
MusicJacket is a prototype teaching system that uses a number of novel ubiquitous technologies and is designed to increase people’s awareness of their posture and assist in learning to play the violin. The system consists of two components: an inertial motion capture system which can track, in real-time, the movement of the bowing arm and the position of the hand holding the violin; and vibrotactile motors placed on the arms and body of the novice player to give real-time feedback. The aim of the system is to support the teacher and to guide the player towards correct playing.

While being based in the labs of the Open University’s Computing Department, the system was developed by an interdisciplinary team of researchers, including physicists, computer scientists, cognitive psychologists, professional violinists as well as an Alexander Technique teacher. We used the explorative method of iterative prototyping and evaluation, at each stage gaining better insight into how this type of tactile feedback can be used by violin players and incrementally refining the system. We used an ‘in the wild’ evaluation method, taking the system to the realistic teaching settings of the school and the home, in order to analyse the system’s usability issues and to explore how this system could be of support to violin teachers. A study with ten children and two violin teachers showed that children as young as six years old were able to react to this type of feedback, and that although individual pupils needed to come to grips with very different aspects of their bowing, the system was flexible enough to offer support on a range of these bowing aspects.
Investigation of the boundary condition of vibrating string is a very important problem in musical acoustics. It is well known that the fundamental frequency of piano string is strictly determined by the type of the string termination. The types of the string support in the piano are different for the bass and treble notes. All the far ends of the piano strings are terminated on the bass and treble bridges, which are the rather complicated resonant systems. The nearest ends of the bass and long treble strings begin from the agraffe that can be considered as an absolutely rigid clamp termination. But the most part of the treble strings starts from the edge of the cast iron frame. These strings turn the rigid edge, and its vibration tone depends on the curvature of this termination.
We investigate the vibrations of the ideal flexible string, which one end is rigidly clamped, and another one is terminated on the curved contact surface. The vibrating string touches repeatedly this termination, and this, in turn, causes the modulation of fundamental frequency of the string, and the train of high frequency oscillations is generated. The problem is studied both analytically, and numerically. The effect of the contact nonlinearity and of the shape of the contact surface on of the spectral structure of the string vibration is considered. The influence of the impact amplitude on the vibration spectra of struck string is discussed.
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