Magnetic Interactions as a Somatosensory Interface Nicola Privato Intelligent Instruments Lab Iceland University of the Arts Reykjavík, Iceland nicola@lhi.is Thor Magnusson Intelligent Instruments Lab Iceland University of the Arts Reykjavík, Iceland thor.magnusson@lhi.is Einar Torfi Einarsson Iceland University of the Arts Reykjavík, Iceland et@lhi.com ABSTRACT Thales is a composed instrument consisting of two hand-held magnetic controllers whose interactions with each other and with other magnets produce the somatosensory manifesta- tion of a tangible interface, that the musician generates and shapes in the act of performing. In this paper we provide a background for the development of Thales by describing the application of permanent magnets in HCI and musical interfaces. We also introduce the instrument’s sound gener- ation based on a neural synthesis model and contextualise the system in relation with the concept of magnetic scores. We report on our preliminary user study and discuss the somatosensory response that characterise Thales, observ- ing the interaction between the opposing magnetic field of the controllers as a tangible magnetic interface. Finally, we investigate its nature from the perspective of performative posthumanist ontologies. Author Keywords Magnets, magnetic interfaces, haptics, somatosensation, neu- ral synthesis CCS Concepts •Hardware → Haptic devices; •Applied computing → Sound and music computing; 1. INTRODUCTION The artistic poetics that characterised the second half of the 20th century have endowed the interpreter with a higher degree of autonomy, compared to the tradition, in relating with the musical material. This is evident in the practices of authors such as Stockhausen, Berio and Pousseur, as dis- cussed in detail in Eco’s Opera Aperta [10]. With composers approaching music notation as a way to prescribe the performer’s gestures rather than as pitch or- ganised in time [15], the mapping of such relations became a crucial element in designing musical interactions [29]. Licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0). Copyright remains with the author(s). NIME’23, 31 May–2 June, 2023, Mexico City, Mexico. Out of the acquired freedom in defining sensible musical parameters and their modalities of representation, new com- positional approaches have emerged [4]. Among such, an increasing number redefine the composer’s and performer’s traditional roles and attributed agencies [24], investigate the relational aspects of the inscription [11], or explicitly sug- gest a dynamic and undefined idea of the score’s situated- ness in relation to the instrument [30]. In describing the progressive embedding of the score within the instrument, Tom´ as and Kaltenbrunner [29] propose the idea of inherent scores, and trace the origin of the concept back to Alvin Lucier, who, in describing the performative practices of the Sonic Art Union, stated that their musical scores were inherent in the electronic circuits developed by the members of the collective [14]. Similarly to inherent scores, the concept of composed in- struments describes the score as incorporated within the instrument itself, in the form of modular mappings whose features define the interaction between a controller and an arbitrary synthesis engine [27]. In such cases, the score is encoded within the dispositif in the form of a defined set of constraints, and is freely explored by the performer through an embodied approach [7]. From this stance, in this paper we introduce Thales,a composed instrument in which, through somatosensory feed- back, the performer experiences the interaction between op- posing magnetic fields as a tangible yet invisible interface: as our preliminary user study shows, the dynamics between Thales’ magnetic fields evoke in the user the impression of interacting with objects of different resistance, shape and materials. In the next section, we frame the use of permanent mag- nets and neural synthesis in musical instruments, as they represent two of the main features of our system, and con- textualise Thales’ composed nature in relation with mag- netic scores, a novel type of inherent scores that, similarly to how Thales generates the interface, encode the inscrip- tion in the form of magnetic fields. 2. BACKGROUND 2.1 Permanent Magnets Permanent magnets constitute a key component of most au- dio electronics, and are extensively incorporated in the de- sign of modern musical instruments and amplification tech- nologies. However, if within HCI the haptic properties of permanent magnetic fields have been explored [31, 8], sim- ilar applications have not been proposed in the design of musical instrument as of yet. A notable example of the use of permanent magnets as key components in the interaction design of an instrument-