Rythme (musique)

Résumé

vignette|Robert Delaunay a voulu exprimer en peinture la notion de rythmes (1932). Le rythme en musique est l'organisation dans le temps des événements musicaux. Il comporte tous les éléments qui permettent de repérer une structure temporelle : espacement, durée, accentuation des sons musicaux. La perception d'un rythme musical implique une forme de répétition de la structure. En musique occidentale, le rythme détermine la durée des notes et le moment où on doit les entendre. Dans la musique classique, une pulsation régulière détermine des temps. Elle permet de mesurer les différentes figures de notes et de silences. Le rythme, la mélodie, le tempo et la nuance sont les quatre principaux éléments de la partition écrite. Dans les traditions musicales hors de l'Europe, le rythme peut se fonder sur des principes différents et impliquer des différences de hauteur ou de timbre des sons, plutôt que leur simple présence ou absence. L'unité de base du rythme est parfois proche de ce qu'on a

Source officielle

https://fr.wikipedia.org/wiki/Rythme_(musique)

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thumb|Tango. D'après l'encyclopédie Larousse, le genre musical est un . Le genre musical est un concept sans limites précises, il est compliqué d'établir une liste exhaustive

Le langage est la capacité d'exprimer une pensée et de communiquer au moyen d'un système de signes (vocaux, gestuel, graphiques, tactiles, olfactifs, etc.) doté d'une sémantique, et le plus souvent d

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This article proposes an original approach to urban events mapping. At the theoretical level, the article is based on rhythmanalysis and recent research on urban rhythms. It contrasts with previous research by departing from everyday rhythms to tackle the specific rhythms of urban events. Drawing on this theoretical framework, the article proposes to analyse the rhythms of the Montreux Jazz Festival. The article proposes two main types of rhythmic scales, linked with the historical development of the Festival and its annual performance. The methodology is based on a mixed method of data collection and an original analysis framework. The analysis of the historical rhythm is carried out based on the analysis of the festival archives and interviews with experts. The analysis uses the Time Machine visualisation device that reveals three processes of urban resonance: the spread, which shows how the festival is integrated into the existing urban fabric; the openness, which shows accessibility; and the grip, which seeks to evaluate the urban sphere of influence of the event. These different visualisations are enriched by the addition of other data, including ticket scanning and commercial transactions that show the alternance between high and low-intensity periods. These allowed us to not only confirm the impact of programming on flows, but also the effects of the wider organisation of the leisure system. The results of the analysis show that the intertwining of the two rhythmic scales produces a hyper-place that resonates both internationally and locally.

2020

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Modeling a diversity of salamander motor behaviors with coupled abstract oscillators and a robot

Jérémie Knüsel

Salamanders are capable of a variety of locomotor behaviors including swimming, underwater stepping, and forward and backward land stepping. According to electromyographic and kinematic recordings of the trunk, each of these behaviors is characterized by a pattern of muscle activation and body curvature with specific values of cycle duration and trunk intersegmental phase lag. A wider, continuous range of intersegmental phase lags is also observed in recordings of isolated spinal cords. Previous models have typically been limited to the generation of two stereotypical behaviors and transitions between them. In contrast, the present work specifically addresses the flexibility of the spinal cord locomotor networks. We investigate how a flexible central pattern generator (CPG) can be modulated by a higher regulation mechanism to generate appropriate patterns of muscle activation. We then look at the effect of the muscles properties and interactions with the environment on the kinematic pattern, and how local proprioceptive feedback can shape the CPG activity. We propose a CPG model based on abstract oscillators that reproduces the main features of recordings from isolated spinal cords, and that scales well to the higher frequencies of locomotion in the intact animal. The model reproduces the distribution of intersegmental phase lags, the correlation between phase lags and cycle frequencies, and the spontaneous switches between slow and fast rhythms. Using numerical simulations of a salamander robot with a simple muscle model and proprioceptive sensory feedback, we show that the CPG model can reproduce the different motor behaviors of the animal. We find that local proprioceptive feedback, together with the mechanical properties of the muscles, can play an important role in reducing the variability of intersegmental phase lags towards values appropriate for locomotion. To validate the simulation results in the real world, we implement the CPG model as a completely distributed controller on a salamander robot. We show that the animal behaviors can be reproduced using only two simple drive signals and local sensory feedback. We find that local proprioceptive sensory feedback can reduce or replace the need for different levels of drive. In particular, good swimming gaits are achieved with the robot using only one level of drive by introducing a strong proprioceptive feedback in the axial oscillators. The model suggests that the same principles govern the shaping of the motor pattern by descending drive signals and local sensory feedback.

EPFL2013

Chargement

Musical grammar describes a set of principles that are used to understand and interpret the structure of a piece according to a musical style. The main topic of this study is grammar induction for harmony --- the process of learning structural principles from the observation of chord sequences. The question how grammars are learnable by induction from sequential data is an instance of the more general question how abstract knowledge is inducible from the observation of data --- a central question of cognitive science. Under the assumption that human learning approximately follows the principles of rational reasoning, Bayesian models of cognition can be used to simulate learning processes. This study investigates what prior knowledge makes it possible to learn musical grammar inductively from Jazz chord sequences using Bayesian models and computational simulations. The theoretical part of the thesis presents how questions about learnability can be studied in a unified framework involving music analysis, cognitive modeling, Bayesian statistics, and computational simulations. A new grammar formalism, called Probabilistic Abstract Context-Free Grammar (PACFG), is proposed that allows for flexible probability models which facilitate the grammar-induction experiments of this study. PACFG can jointly model multiple musical dimensions such as harmony and rhythm, and can use coordinate ascent variational inference for grammar learning. The empirical part of the thesis reports supervised and unsupervised grammar-learning experiments. To train and evaluate grammar models, a ground-truth dataset of hierarchical analyses of complete Jazz standards, called the Jazz Harmony Treebank (JHT), was created. The supervised grammar-learning experiments, in which grammars for Jazz harmony are learned from the JHT analyses, show that jointly modeling harmony and rhythm significantly improves the grammar models' prediction of the ground truth. The performance and robustness of the grammars are further improved by a transpositionally invariant parameterization of rule probabilities. Following the supervised grammar learning, unsupervised grammar learning was performed by inducing harmony grammars merely from Jazz chord sequences, without the observation of the JHT trees. The results show that the best induced grammar performs similarly well as the best supervised grammar. In particular, the goal-directedness of functional harmony does not need to be assumed a priori, but can be learned without usage of music-specific prior knowledge. The findings of this thesis show that general prior knowledge enables an ideal learner to acquire abstract musical principles by statistical learning. In conclusion, it is plausible that much aspects of musical grammar have been learned by Jazz musicians and listeners, instead of being innate predispositions or explicitly taught concepts. This thesis is moreover embedded into the context of empirical music research and digital humanities. Current studies either describe complex musical structures qualitatively or investigate simpler aspects quantitatively. The computational models developed in this thesis demonstrate that deep insights into music and statistical analyses are not mutually exclusive. They enable a new kind of data-driven music theory and musicology, for instance through comparative analyses of musical grammar for different styles such as Jazz, Rock, and Western classical music.

EPFL2020

Chargement

EPFL2020

Modeling a diversity of salamander motor behaviors with coupled abstract oscillators and a robot

Jérémie Knüsel

EPFL2013