Download A general-purpose deep learning approach to model time-varying audio effects Audio processors whose parameters are modified periodically over time are often referred as time-varying or modulation based audio effects. Most existing methods for modeling these type of effect units are often optimized to a very specific circuit and cannot be efficiently generalized to other time-varying effects. Based on convolutional and recurrent neural networks, we propose a deep learning architecture for generic black-box modeling of audio processors with long-term memory. We explore the capabilities of deep neural networks to learn such long temporal dependencies and we show the network modeling various linear and nonlinear, time-varying and time-invariant audio effects. In order to measure the performance of the model, we propose an objective metric based on the psychoacoustics of modulation frequency perception. We also analyze what the model is actually learning and how the given task is accomplished.
Download Real-time 3D Ambisonics using Faust, Processing, Pure Data, and OSC This paper presents several digital signal processing (DSP) tools for the real-time synthesis of a 3D sound pressure field using Ambisonics technologies. The spatialization of monophonic signal or the reconstruction of natural 3D recorded sound pressure fields is considered. The DSP required to generate the loudspeaker signals is implemented using the FAUST programming language. FAUST enables and simplifies the compilation of the developed tools on several architectures and on different DSP tool format. In this paper, a focus is made on the near-field filters implementation which allows for the encoding of spherical waves with distance information. The gain variation with distance is also taken into account. The control of the synthesis can be made by software controllers or hardware controllers, such as joystick, by the mean of P URE DATA and O PEN S OUND C ONTROL (OSC) messages. A visual feedback tool using the P ROCESSING programming language is also presented in the most recent implementation. The aim of this research derives from a larger research project on physically-accurate sound field reproduction for simulators in engineering and industrial applications.
Download Musical Gestures and Audio Effects Processing We introduce the notion of musical gestures as time varying measurements which identify the audio input stream’s musical skeleton without attempting to implement any involved model of musical understanding. Living comfortably at an intermediate level of abstraction between wave forms and music transcriptions, these musical gestures are used to control the behavior of an audio processing module. The resulting scheme qualifies as an audio effects processing system as it essentially transforms an audio stream into another.
Download A Csound Opcode for a Triode Stage of a Vacuum Tube Amplifier The Csound audio programming language adheres to the inputoutput paradigm and provides a large number of specialized commands (called opcodes) for processing output signals from input signals. Therefore it is not directly suitable for component modeling of analog circuitry. This contribution describes an attempt to virtual analog modeling and presents a Csound opcode for a triode stage of a vacuum tube amplifier. Externally it communicates with other opcodes via input and output signals at the sample rate. Internally it uses an established wave digital filter model of a standard triode. The opcode is available as library module.
Download Sound Morphing by Audio Descriptors and Parameter Interpolation We present a strategy for static morphing that relies on the sophisticated interpolation of the parameters of the signal model and the independent control of high-level audio features. The source and target signals are decomposed into deterministic, quasi-deterministic and stochastic parts, and are processed separately according to sinusoidal modeling and spectral envelope estimation. We gain further intuitive control over the morphing process by altering the interpolated spectrum according to target values of audio descriptors through an optimization process. The proposed approach leads to convincing morphing results in the case of sustained or percussive, harmonic and inharmonic sounds of possibly different durations.
Download Comparing Acoustic and Digital Piano Actions: Data Analysis and Key Insights The acoustic piano and its sound production mechanisms have been
extensively studied in the field of acoustics. Similarly, digital piano synthesis has been the focus of numerous signal processing
research studies. However, the role of the piano action in shaping the dynamics and nuances of piano sound has received less
attention, particularly in the context of digital pianos. Digital pianos are well-established commercial instruments that typically use
weighted keys with two or three sensors to measure the average
key velocity—this being the only input to a sampling synthesis
engine. In this study, we investigate whether this simplified measurement method adequately captures the full dynamic behavior of
the original piano action. After a brief review of the state of the art,
we describe an experimental setup designed to measure physical
properties of the keys and hammers of a piano. This setup enables
high-precision readings of acceleration, velocity, and position for
both the key and hammer across various dynamic levels. Through
extensive data analysis, we examine their relationships and identify
the optimal key position for velocity measurement. We also analyze
a digital piano key to determine where the average key velocity is
measured and compare it with our proposed optimal timing. We
find that the instantaneous key velocity just before let-off correlates
most strongly with hammer impact velocity, indicating a target
for improved sensing; however, due to the limitations of discrete
velocity sensing this optimization alone may not suffice to replicate
the nuanced expressiveness of acoustic piano touch. This study
represents the first step in a broader research effort aimed at linking
piano touch, dynamics, and sound production.
Download State-Space Representation for Digital Waveguide Networks of Lossy Flared Acoustic Pipes This paper deals with digital waveguide modeling of wind instruments. It presents the application of state-space representations to the acoustic model of Webster-Lokshin. This acoustic model describes the propagation of longitudinal waves in axisymmetric acoustic pipes with a varying cross-section, visco-thermal losses at the walls, and without assuming planar or spherical waves. Moreover, three types of discontinuities of the shape can be taken into account (radius, slope and curvature), which can lead to a good fit of the original shape of pipe. The purpose of this work is to build low-cost digital simulations in the time domain, based on the Webster-Lokshin model. First, decomposing a resonator into independent elementary parts and isolating delay operators lead to a network of input/output systems and delays, of KellyLochbaum network type. Second, for a systematic assembling of elements, their state-space representations are derived in discrete time. Then, standard tools of automatic control are used to reduce the complexity of digital simulations in time domain. In order to validate the method, simulations are presented and compared with measurements.
Download Digital Morphophone Environment. Computer Rendering of a Pioneering Sound Processing Device This paper introduces a digital reconstruction of the morphophone,
a complex magnetophonic device developed in the 1950s within
the laboratories of the GRM (Groupe de Recherches Musicales)
in Paris. The analysis, design, and implementation methodologies
underlying the Digital Morphophone Environment are discussed.
Based on a detailed review of historical sources and limited
documentation – including a small body of literature and, most
notably, archival images – the core operational principles of the
morphophone have been modeled within the MAX visual programming environment. The main goals of this work are, on the one
hand, to study and make accessible a now obsolete and unavailable
tool, and on the other, to provide the opportunity for new explorations in computer music and research.