La présente thèse étudie le rôle de l’instrumentiste – en prenant comme exemple le cas du guitariste – au sein du théâtre musical contemporain. L’étude se centre sur la discussion esthétique autour du rôle de cet instrumentiste dans la construction d’une nouvelle instrumentalité, en rapport à une nouvelle théâtralité. Elle est basée sur La tragique histoire du nécromancien Hieronimo et de son miroir de Georges Aperghis, Lorenzaccio et Nuovo scenario da Lorenzaccio de Sylvano Bussotti, We come to the river de Hans Werner Henze, Sonant et Serenade de Mauricio Kagel, …Zwei Gefühle… et Das Mädchen mit den Schwefelhölzern de Helmut Lachenmann. A l’intérieur de cette théâtralité renouvelée, l’idée de représentation théâtrale est presque toujours abolie : à la place, le récit est assumé par la totalité des interprètes, y compris le guitariste. Par conséquent, la théâtralité se relie au jeu instrumental surtout en ce que le geste instrumental lui-même est valorisé. Ainsi, l’exploration des possibilités instrumentales de la guitare acquiert une dimension ludique (approcher l’instrument en tant qu’objet, avec de l’humour, en extraire de nouveaux sons). Cette notion de « jeu » intervient sur la manière d’envisager l’interprète. Ainsi les œuvres étudiées, chacune à sa manière, attribuent à l’interprète lui-même la source principale de leur théâtralité. La manière comme ce théâtre aborde la guitare comporte un nombre important de références à différents univers musicaux (le rock’n roll, la musique espagnole…) Enfin, le potentiel timbrique de cet instrument est aussi exploré. Ce rapport référentiel à l’instrument révèle un processus existentiel de mise en abîme. / This thesis examines the role of the musician - taking as an example the guitarist - in the contemporary musical theater. The study focuses on the aesthetic discussion of the role of the instrumentalist in the construction of a new instrumentality in relation to a new theatricality. It studies the works La tragique histoire du nécromancien Hieronimo et de son miroir by Georges Aperghis, Lorenzaccio and Nuovo scenario da Lorenzaccio by Sylvano Bussotti, We come to the river by Hans Werner Henze, Sonant and Serenade by Mauricio Kagel, …Zwei Gefühle… and Das Mädchen mit den Schwefelhölzern by Helmut Lachenmann. Within this renewed theatricality, the idea of theatrical representation is almost always abolished : instead, the story is carried by all performers, including the guitarist. Therefore, the inner theatricality of instrumental playing valorizes the instrumental gesture. Thus, the exploration of instrumental possibilities of the guitar becomes something playful ( as to approach the instrument as an object, with humour, and to extract new sounds from it). This notion of "playfulness" is determinant on the approach to the interpreter. Each studied score in its own way attribute the interpreter itself the main source of their theatricality. These musical theatres make a large number of references to various musical universes associated with the guitar ( rock'n roll , Spanish music ... ) Finally, the potential of guitar’s colour palette is also explored. These references relative to the instrument reveal a process of existential metalanguage.

A constantly growing corpus of interdisciplinary studies support the idea that music is a complex multimodal medium that is experienced not only by means of sounds but also through body movement. From this perspective, musical instruments can be seen as technological objects coupled with a repertoire of performance gestures. This repertoire is part of an ecological knowledge shared by musicians and listeners alike. It is part of the engine that guides musical experience and has a considerable expressive potential. This thesis explores technical and conceptual issues related to the analysis and creative use of music-related body movements in instrumental music performance. The complexity of this subject required an interdisciplinary approach, which includes the review of multiple theoretical accounts, quantitative and qualitative analysis of data collected in motion capture laboratories, the development and implementation of technologies for the interpretation and interactive use of motion data, and the creation of short musical pieces that actively employ the movement of the performers as an expressive musical feature. The theoretical framework is informed by embodied and enactive accounts of music cognition as well as by systematic studies of music-related movement and expressive music performance. The assumption that the movements of a musician are part of a shared knowledge is empirically explored through an experiment aimed at analysing the motion capture data of a violinist performing a selection of short musical excerpts. A group of subjects with no prior experience playing the violin is then asked to mime a performance following the audio excerpts recorded by the violinist. Motion data is recorded, analysed, and compared with the expert’s data. This is done both quantitatively through data analysis xii as well as qualitatively by relating the motion data to other high-level features and structures of the musical excerpts. Solutions to issues regarding capturing and storing movement data and its use in real-time scenarios are proposed. For the interactive use of motion-sensing technologies in music performance, various wearable sensors have been employed, along with different approaches for mapping control data to sound synthesis and signal processing parameters. In particular, novel approaches for the extraction of meaningful features from raw sensor data and the use of machine learning techniques for mapping movement to live electronics are described. To complete the framework, an essential element of this research project is the com- position and performance of études that explore the creative use of body movement in instrumental music from a Practice-as-Research perspective. This works as a test bed for the proposed concepts and techniques. Mapping concepts and technologies are challenged in a scenario constrained by the use of musical instruments, and different mapping ap- proaches are implemented and compared. In addition, techniques for notating movement in the score, and the impact of interactive motion sensor systems in instrumental music practice from the performer’s perspective are discussed. Finally, the chapter concluding the part of the thesis dedicated to practical implementations describes a novel method for mapping movement data to sound synthesis. This technique is based on the analysis of multimodal motion data collected from multiple subjects and its design draws from the theoretical, analytical, and practical works described throughout the dissertation. Overall, the parts and the diverse approaches that constitute this thesis work in synergy, contributing to the ongoing discourses on the study of musical gestures and the design of interactive music systems from multiple angles.