Henri Penttinen

Model-based sound synthesis of the guqin

This paper presents a model-based sound synthesis algorithm for the Chinese plucked string instrument called the guqin. The instrument is fretless, which enables smooth pitch glides from one note to another. A version of the digital waveguide synthesis approach is used, where the string length is time-varying and its energy is scaled properly. A body model filter is placed in cascade with the string model. Flageolet tones are synthesized with the so-called ripple filter structure, which is an FIR comb filter in the delay line of a digital waveguide model. In addition, signal analysis of recorded guqin tones is presented. Friction noise produced by gliding the finger across the soundboard has a harmonic structure and is proportional to the gliding speed. For pressed tones, one end of a vibrating string is terminated either by the nail of the thumb or a fingertip. The tones terminated with a fingertip decay faster than those terminated with a thumb. Guqin tones are slightly inharmonic and they exhibit phantom partials. The synthesis model takes into account these characteristic features of the instrument and is able to reproduce them. The synthesis model will be used for rule based synthesis of guqin music.

Sound synthesis of the harpsichord using a computationally efficient physical model

A sound synthesis algorithm for the harpsichord has been developed by applying the principles of digital waveguide modeling. A modification to the loss filter of the string model is introduced that allows more flexible control of decay rates of partials than is possible with a one-pole digital filter, which is a usual choice for the loss filter. A version of the commuted waveguide synthesis approach is used, where each tone is generated with a parallel combination of the string model and a second-order resonator that are excited with a common excitation signal. The second-order resonator, previously proposed for this purpose, approximately simulates the beating effect appearing in many harpsichord tones. The characteristic key-release thump terminating harpsichord tones is reproduced by triggering a sample that has been extracted from a recording. A digital filter model for the soundboard has been designed based on recorded bridge impulse responses of the harpsichord. The output of the string models is injected in the soundboard filter that imitates the reverberant nature of the soundbox and, particularly, the ringing of the short parts of the strings behind the bridge.

Sound and Music Computing: Research Trends and Some Key Issues

Abstract This contribution attempts to give an overview of current research trends and open research problems in the rich field of Sound and Music Computing (SMC). To that end, the field is roughly divided into three large areas related to Sound, Music, and Interaction, respectively, and within each of these, major research trends are briefly described. In addition, for each sub-field a small number of open research (or research strategy) issues are identified that should be addressed in order to further advance the SMC field.

Analysis and modeling of piano sustain-pedal effects

This paper describes the main features of the sustain-pedal effect in the piano through signal analysis and presents an algorithm for simulating the effect. The sustain pedal is found to increase the decay time of partials in the middle range of the keyboard, but this effect is not observed in the case of the bass and treble tones. The amplitude beating characteristics of piano tones are measured with and without the sustain pedal engaged, and amplitude envelopes of partial overtone decay are estimated and displayed. It is found that the usage of the sustain pedal introduces interesting distortions of the two-stage decay. The string register response was investigated by removing partials from recorded tones; it was observed that as the string register is free to vibrate, the amount of sympathetic vibrations is increased. The synthesis algorithm, which simulates the string register, is based on 12 string models that correspond to the lowest tones of the piano. The algorithm has been tested with recorded piano tones without the sustain pedal. The objective and subjective results show that the algorithm is able to approximately reproduce the main features of the sustain-pedal effect.

Acoustic sound from the electric guitar using DSP techniques

The electric guitar has been developed to withstand electric amplification and utilize (mostly analog) signal processing in order to create a multitude of timbres and sound types. Sometimes it would be desirable to play the same electric guitar, yet with a sound that resembles a good acoustic guitar or some other member of the plucked string instrument family. In this study we have investigated DSP techniques that can be used to shape the magnetic pickup output of the electric guitar to simulate acoustic instruments. This includes linear filtering for body simulation, time-varying modulation to generate beating of the harmonic components, and techniques to simulate the general temporal envelope of the plucked notes.

Parametric electric guitar synthesis

The electric guitar is one of the most common musical instruments today. Several synthesis algorithms have been created to synthesize its sound (Sullivan 1990; Karjalainen et al. 2006; Pakarinen, Puputti, and Valimaki 2008; Smith 2008). However, these previous synthesis models lack a few features that contribute to, or alter, the characteristic electric guitar tone. Firstly, the magnetic pickup used in electric guitars alters the sound radically. The magnetic pickup acts as a bandpass filter and causes a comb filter–like effect as a function of its position (Jungmann 1994). In addition, the response of the magnetic pickup has been found to be inharmonic, as are the vibrations of the string. Secondly, when using a distortion effect, the details of the attack and the sustain part of a tone are brought to an audible level, which is not the case with acoustic instruments. This is caused by the radically increased gain (0–120 dB) and the inherent compression of the distortion effect. Thirdly, the instrument can be played very expressively: The player has total control of the plucking event (plucking angle, force, and width) and can bend the string to alter the pitch. This article proposes a new parametric synthesis model that enables the creation of these sonic features. The synthesis model is based on the waveguide method (Jaffe and Smith 1983; Smith 1992; Karjalainen, Valimaki, and Tolonen 1998) with novel alterations. A new excitation model is introduced that recreates the plectrum scrape and the first displacement pulse created during the plucking event. The excitation model also accounts for different plucking forces, and the angle of the virtual plectrum is controllable. The string model is

Acoustic guitar plucking point estimation in real time

The algorithm estimates the plucking point of guitar tones obtained with an undersaddle pickup. This problem is approached in the time domain by applying autocorrelation estimation. This work extends a recently developed algorithm and brings it to a practical and sufficiently robust level. Improvements have been made to the onset detection part of the algorithm. The algorithm also enables a new way to control, for example, audio effect parameters in real time by simply changing the plucking point. The paper discusses these issues and the real-time implementation in the Pd environment. In tests, the real-time implementation achieved a 96% hit rate while the estimation error remains smaller than one centimeter, except for a few outliers. Audio samples and a Pd implementation of the algorithm are available on-line at www.acoustics.hut.fi/demos/plucking-point/.

A digital waveguide-based approach for Clavinet modeling and synthesis

The Clavinet is an electromechanical musical instrument produced in the mid-twentieth century. As is the case for other vintage instruments, it is subject to aging and requires great effort to be maintained or restored. This paper reports analyses conducted on a Hohner Clavinet D6 and proposes a computational model to faithfully reproduce the Clavinet sound in real time, from tone generation to the emulation of the electronic components. The string excitation signal model is physically inspired and represents a cheap solution in terms of both computational resources and especially memory requirements (compared, e.g., to sample playback systems). Pickups and amplifier models have been implemented which enhance the natural character of the sound with respect to previous work. A model has been implemented on a real-time software platform, Pure Data, capable of a 10-voice polyphony with low latency on an embedded device. Finally, subjective listening tests conducted using the current model are compared to previous tests showing slightly improved results.

Measuring and evaluating a louder design of the musical instrument kantele

The kantele is a musical instrument excited by plucking. It is an ancient instrument, which is still used in traditional folk music in Finland, Northwest Russia, and the Baltic countries. This paper discusses analysis and measurement results of a modified kantele, designed to have an increased loudness. The design rules to make the modified kantele louder are also proposed. The conducted measurements confirm and support the proposed design rules. The main features of the traditional design of the kantele are described, so that the presentation of the design rules and analysis results could be understood. The design rules to make a plucked string instrument louder are (1) increase the tension of the string, (2) increase the radiation surface, and (3) isolate the top plate from the sound-box with an air gap. To some extent rules (1) and (2) are straightforward and familiar for most musical acousticians. In contrast, rule (3) is more evolved and unique, since it enables a freely vibrating top plate. To confirm the design rules, the traditional design is compared with the new one, through several methodological aspects. Results from the analysis are drawn from both analytical treatments and acoustical measurements. A listening test was also conducted and the results of this test support the assumption of an increase in loudness for the new kantele design. More specifically, on the average loud plucks of the modified design are perceived as 3 dB louder than in the traditional design. Furthermore, on certain strings the loud plucks are perceived as 6 dB louder. The proposed design ideas can also be applied to other string instruments.