Chris Chafe

Neural Dynamics of Event Segmentation in Music: Converging Evidence for Dissociable Ventral and Dorsal Networks

The real world presents our sensory systems with a continuous stream of undifferentiated information. Segmentation of this stream at event boundaries is necessary for object identification and feature extraction. Here, we investigate the neural dynamics of event segmentation in entire musical symphonies under natural listening conditions. We isolated time-dependent sequences of brain responses in a 10 s window surrounding transitions between movements of symphonic works. A strikingly right-lateralized network of brain regions showed peak response during the movement transitions when, paradoxically, there was no physical stimulus. Model-dependent and model-free analysis techniques provided converging evidence for activity in two distinct functional networks at the movement transition: a ventral fronto-temporal network associated with detecting salient events, followed in time by a dorsal fronto-parietal network associated with maintaining attention and updating working memory. Our study provides direct experimental evidence for dissociable and causally linked ventral and dorsal networks during event segmentation of ecologically valid auditory stimuli.

JackTrip: Under the Hood of an Engine for Network Audio

Abstract The design of a platform for bi-directional musical performance using modern Wide area networks (WANs) poses several challenges that are different from related applications, e.g. synchronous local area network (LAN) studio systems or uni-directional WAN streaming. The need to minimize as much as possible audio latency and also maximize audio quality requires specific strategies which are informed, in part, by musical decisions. We present some of the key design elements of the JackTrip application which has evolved through several years of deployment in musical work over wide area networks.

Effect of Temporal Separation on Synchronization in Rhythmic Performance

A variety of short time delays inserted between pairs of subjects were found to affect their ability to synchronize a musical task. The subjects performed a clapping rhythm together from separate sound-isolated rooms via headphones and without visual contact. One-way time delays between pairs were manipulated electronically in the range of 3 to 78 ms. We are interested in quantifying the envelope of time delay within which two individuals produce synchronous performances. The results indicate that there are distinct regimes of mutually coupled behavior, and that ‘natural time delay’—delay within the narrow range associated with travel times across spatial arrangements of groups and ensembles—supports the most stable performance. Conditions outside of this envelope, with time delays both below and above it, create characteristic interaction dynamics in the mutually coupled actions of the duo. Trials at extremely short delays (corresponding to unnaturally close proximity) had a tendency to accelerate from anticipation. Synchronization lagged at longer delays (larger than usual physical distances) and produced an increasingly severe deceleration and then deterioration of performed rhythms. The study has implications for music collaboration over the Internet and suggests that stable rhythmic performance can be achieved by ‘wired ensembles’ across distances of thousands of kilometers.

TAPPING INTO THE INTERNET AS AN ACOUSTICAL AND MUSICAL MEDIUM

Network audio technology transforms advanced networks into a new kind of sound propagation medium, with its own properties compared to air, water, or solids. Three areas of research are described: 1) methods for using your ears for monitoring quality-of-service (QoS) of networks supporting high-quality, real-time, interactive, bidirectional flows; 2) new musical practices being made in the medium; and 3) a discussion of human factors affected by some unique acoustical properties of the medium.

Physical model synthesis with application to Internet acoustics

Distributed physical models of musical instruments have been used to acoustically “ping” Internet connections between two network hosts. Sound waves propagated through Internet acoustics behave just as in air, water or along a stretched string. In this case, a musical synthesis technique creates waves on the Internet path between two hosts. When waves recirculate between two endpoints, a musical tone is created if the round trip travel time lies within the range of our pitch sense (roughly 250µs to 50ms). The resulting tones provide a quick and intuitive evaluation of quality of service (QoS), displaying its significant aspects including latency, jitter and packet loss. Stable, clear tones with high pitch indicate good end-to-end capabilities that a path must support for immersive, real-time applications. A “network harp” recently demonstrated 320 synthesized strings oscillating across the Western half of the Internet2 Abilene Network.

Jacktrip/soundwire meets server farm

Even though bidirectional, high-quality and low-latency audio systemsfor networkperformanceare available, the complexity involved in setting up remote sessions needs better toolsandmethodsto asses andtunenetworkparameters. We present an implementation of a system to intuitively evaluate the Quality of Service (QoS) onbest effortnetworks. In our implementation,musicians are able to connect to a multi-client server and tune the parameters of a connection using direct “auditory displays.” The server can scale up to hundredsof users by taking advantageof modernmulti-core machinesand multi-threadedprogramingtechniques. It also serves as a central “mixing hub”when network performance involves several participants.

Analysis of Flute Control Parameters : A Comparison Between a Novice and an Experienced Flautist

The sound produced by flutes depends not only on the physical characteristics of the instrument but also on the control exerted by the musician. The latter is very important in some instruments of the flute family, especially in those where the air jet is shaped with the lip of the player. Some of the most relevant parameters controlled by the flautist, such as the distance from the lips to the sharp edge, the shape of the lips hole and the speed of the jet, are experimentally measured in this paper. Data produced by an experienced and a novice flautist are collected, analyzed and compared. Subjects are studied under normal musical playing conditions, playing phrases made out of simple musical intervals with subjective dynamics. Images of performers lips are taken together with measurements of the blowing pressure and the sound radiated by the instrument. Data analysis shows remarkable differences between the two subjects. The optimized coordination of several parameters in order to obtain a desired musical response, coupling between performers mouth and the instrument, as well as the efficient use of the available resources are some of the differences observed.

Cyberinstruments via Physical Modeling Synthesis: Compositional Applications

ABSTRACT This paper details compositional approaches in music for cyberinstruments by means of physical modeling synthesis. Although the focus is on compositions written with the models simulated by the digital waveguides, modal synthesis and mass-spring-damper algorithms, music written with other modeling techniques is also reviewed.

An Overview on Networked Music Performance Technologies

Networked music performance (NMP) is a potential game changer among Internet applications, as it aims at revolutionizing the traditional concept of musical interaction by enabling remote musicians to interact and perform together through a telecommunication network. Ensuring realistic performance conditions, however, constitutes a significant engineering challenge due to the extremely strict requirements in terms of network delay and audio quality, which are needed to maintain a stable tempo, a satisfying synchronicity between performers and, more generally, a high-quality interaction experience. In this paper, we offer a review of the psycho-perceptual studies conducted in the past decade, aimed at identifying latency tolerance thresholds for synchronous real-time musical performance. We also provide an overview of hardware/software enabling technologies for NMP, with a particular emphasis on system architecture paradigms, networking configurations, and applications to real use cases.

Oxygen flute: A computer music instrument that grows

Abstract The quality of the air we breathe depends on a balance of plant and animal life. Oxygen Flute is an interactive computer music environment that makes the exchange of gases audible. Gallery visitors enter a chamber with bamboo and four continuously performing (digitally modeled) flutes. Patterns in levels of carbon dioxide measured inside the chamber create the music. The computer flutes are played both in real time and from the accumulated history of fluctuations recorded in the space. The flute models are simulations of 9,000 year-old bone flutes from China.