Download Discretization of the '59 Fender Bassman Tone Stack
The market for digital modeling guitar amplifiers requires that the digital models behave like the physical prototypes. A component of the iconic Fender Bassman guitar amplifier, the tone stack circuit, filters the sound of the electric guitar in a unique and complex way. The controls are not orthogonal, resulting in complicated filter coefficient trajectories as the controls are varied. Because of its electrical simplicity, the tone stack is analyzed symbolically in this work, and digital filter coefficients are derived in closed form. Adhering to the technique of virtual analog, this procedure results in a filter that responds to user controls in exactly the same way as the analog prototype. The general expressions for the continuous-time and discrete-time filter coefficients are given, and the frequency responses are compared for the component values of the Fender ’59 Bassman. These expressions are useful implementation and verification of implementations such as the wave digital filter.
Download On the Use of Volterra Series for Efficient Real-Time Simulations of Weakly Nonlinear Analog Audio Devices: Application to the Moog Ladder Filter
In this paper, we show how the formalism of the Volterra series can be used to represent the nonlinear Moog ladder filter. The analog circuit is analyzed to produce a set of governing differential equations. The Volterra kernels of this system are solved from simple algebraic equations. They define an exact decomposition of the system. An identification procedure leads to structures composed of linear filters, sums and instantaneous products of signals. Finally, a discrete-time realization of the truncated series, which guarantees no aliasing, is performed.
Download Robust Design of Very High-Order Allpass Dispersion Filters
A nonparametric allpass filter design method is presented for matching a desired group delay as a function of frequency. The technique is useful in physical modeling synthesis of musical instruments and emulation of audio effects devices exhibiting dispersive wave propagation. While current group delay filter design methods suffer from numerical difficulties except at low filter orders, the technique presented here is numerically robust, producing an allpass filter in cascaded biquad form, and with the filter poles following a smooth loop within the unit circle. The technique was inspired by the observation that a pole-zero pair arranged in allpass form contributes exactly 2π radians to the integral of group delay around the unit circle, regardless of the (stable) pole location. To match a given group delay characteristic, the method divides the frequency axis into sections containing 2π total area under the desired group-delay curve, and assigns a polezero allpass pair to each. In this way, the method incorporates an order selection technique, and by adding a pure delay to the desired group delay, allows the trading of increased filter order for improved fit to the frequency-dependent group delay. Design examples are given for modeling the group delay of a dispersive string (such as a piano string), and a dispersive spring, such as in a spring reverberator.
Download Consistency of Timbre Patterns in Expressive Music Performance
Musical interpretation is an intricate process due to the interaction of the musician’s gesture and the physical possibilities of the instrument. From a perceptual point of view, these elements induce variations in rhythm, acoustical energy and timbre. This study aims at showing the importance of timbre variations as an important attribute of musical interpretation. For this purpose, a general protocol aiming at emphasizing specific timbre patterns from the analysis of recorded musical sequences is proposed. An example of the results obtained by analyzing clarinet sequences is presented, showing stable timbre variations and their correlations with both rhythm and energy deviations.
Download Real-Time Detection of Finger Picking Musical Structures
MIDIME is a software architecture that houses improvisational agents that react to MIDI messages from a finger-picked guitar. They operate in a pipeline whose first stage converts MIDI messages to a map of the state of instrument strings over time, and whose second stage selects rhythmic, modal, chordal, and melodic interpretations from the superposition of interpretations latent in the first stage. These interpretations are nondeterministic, not because of any arbitrary injection of randomness by an algorithm, but because guitar playing is nondeterministic. Variations in timing, tuning, picking intensity, string damping, and accidental or intensional grace notes can affect the selections of this second stage. The selections open to the second stage, as well as the third stage that matches second stage selections to a stored library of composition fragments, reflect the superposition of possible perceptions and interpretations of a piece of music. This paper concentrates on these working analytical stages of MIDIME. It also outlines plans for using the genetic algorithm to develop improvisational agents in the final pipeline stage.
Download Using Visual Textures for Sonic Textures Production and Control
This work takes place in the framework of a global research on the synthesis of sonic textures and its control through a gesturebased interaction in a musical practice. In this paper we present different strategies to link visual and sonic textures using similar synthesis processes; theoretical considerations underlying to this problematic are firstly exposed and several personal realizations, illustrating different approaches to design a gesturally controlled audio-visual system, are then described.
Download Graphic Equalizer Design Using Higher-Order Recursive Filters
A straight-forward design of graphic equalizers with minimumphase behavior based on recently developed higher-order bandshelving filters is presented. Due to the high filter order, the gain in one band is almost completely independent from the gain in the other bands. Although no special care will be taken to design filters with complementary edges except for a suitable definition of the cut-off frequencies, the resulting amplitude deviation in the transitional region between the bands will be sufficiently low for many applications.
Download Performance-Driven Control for Sample-Based Singing Voice Synthesis
In this paper we address the expressive control of singing voice synthesis. Singing Voice Synthesizers (SVS) traditionally require two types of inputs: a musical score and lyrics. The musical expression is then typically either generated automatically by applying a model of a certain type of expression to a high-level musical score, or achieved by manually editing low-level synthesizer parameters. We propose an alternative method, where the expression control is derived from a singing performance. In a first step, an analysis module extracts expressive information from the input voice signal, which is then adapted and mapped to the internal synthesizer controls. The presented implementation works in an off-line manner processing user input voice signals and lyrics using a phonetic segmentation module. The main contribution of this approach is to offer a direct way of controlling the expression of SVS. The further step is to run the system in real-time. The last section of this paper addresses a possible strategy for real-time operation.
Download Parameterized Morphing as a Mapping Technique for Sound Synthesis
We present a novel mapping technique for sound synthesis. The technique extends the familiar concept of morphing to the domain of synthesis parameters. A morph between defined points in the parameter space representing desirable sounds is itself parameterized with high-level controls. The choice of end points of the morph and the extent of the morph are used as input handles to map arbitrary control signals to the synthesis parameters. Additional off-line methods control the interpolation functions and selection of parameter points. We discuss a tool to allow creation, manipulation and usage of such mappings.
Download Examining Design Goals of Digital Musical Instruments
This paper describes the adaptation of an existing model of human information processing for the categorization of digital musical instruments in terms of performance context and behavior. It further presents a visualization intended to aid the analysis of existing DMIs and the design of new devices. Three new interfaces constructed by the authors are examined within this framework to illustrate its utility.