ACQUISITION OF VIOLIN INSTRUMENTAL GESTURES USING A COMMERCIAL EMF TRACKING DEVICE Esteban Maestre, Jordi Bonada, Merlijn Blaauw Alfonso P´ erez, Enric Guaus Music Technology Group, Universitat Pompeu Fabra Ocata 1, Barcelona, SPAIN {emaestre,jbonada,mblaauw,aperez,eguaus}@iua.upf.edu ABSTRACT This paper presents a method for the acquisition of vio- lin instrumental gesture parameters by using a commercial two-sensor 3D tracking system based on electro-magnetic field (EMF) sensing. The methodolgy described here is suitable for acquiring instrumental gesture parameters of any bowed-string instrument, and has been devised by pay- ing attention to intrusion, flexibility, and robustness. Af- ter reviewing relevant related work in the field, we give an overview of the application context, pointing out some ba- sic needs to be fulfilled for our research purposes. Then, we present the steps for calibrating the system, followed by details on the computation of a number of relevant in- strumental gesture parameters. The use of a number of the extracted parameters to perform score-performance align- ment and database automatic annotation is also outlined. Finally, we conclude stating next steps in using acquired data, along with further developments of the methodology. 1. INTRODUCTION Interaction between performer and instrument during a performance gets more complex when dealing with excitation- continuous musical instruments, as it is the case of bowed- string family, which is often considered among the most articulate and expressive musical instrument family. Cap- turing violin instrumental gestures parameters (i.e. di- rectly involved in sound production mechanisms) is of great interest, as there have been already a number of works dealing with this issue and with the aim of appyling results both to performance and to research (see Section 2). Par- ticularly for our research purposes, focused on the study of instrumental gestures in violin traditional performance in order to apply them for synthesis, it is important to be able to acquire relevant timbre-related parameters with enough accuracy, while not affecting the performance habits. In this paper, we present a new approach for acquir- ing violin instrumental gesture parameters in real-time. This approach is based on the use of electro-magnetic field (EMF) sensing (two wired sensors), by using one of the commercially available solutions. The main requirements that we forecasted when devising the proposed method- ology were: (1) to have a system capable of gathering as many instrumental gesture parameters as possible, (2) to be accurate, (3) to be easily attached to any violin/bow, and (4) to present a small effect on the instrument playa- bility. As a first step towards our research goals, we use the acquired parameters for automatically annotating a per- formance database by applying a custom score-performance alignment procedure. The paper is structured as follows. First, we offer an outlook to the related work in the field, highlighting the main differences with the approach presented here. Then, we put our work into context, pointing out our research purposes, and discussing the fulfillment of our application requirements. Section 4 outlines the calibration proce- dure, while Section 5 gives the details of the computation of a number of instrumental gesture parameters. In Sec- tion 6, we present the score-alignment procedure devised for annotating our database. We conclude by discussing further developments of the methodology and future uses of our gathered data. 2. RELATED WORK Research in capturing gestures involved in sound produc- tion mechanisms of bowed-string instruments has led to diverse successful approaches that can be found in the lit- erature since already the eighties. In [1] and [2], Askenfelt presents methods for mea- suring bow motion and bow force using diverse custom electronic devices attached to both the violin and the bow. The bow transversal position is measured by means of a thin resistance wire inserted among the bow hairs, while for the bow-bridge distance, the strings are electrified, so that the contact position with the resistance wire among the bow hairs is detected. For the bow pressure, four strain gages (two at the tip and two at the frog) are used. A different approach was taken in [6], where Paradiso and Gershenfeld measured bow displacement by means of oscillators driving antennas (electric field sensing). In a first application carried out for cello, a resistive strip at- tached to the bow was driven by a mounted antenna be- hind the bridge, resulting as well into a wired bow. Af- terward, in the violin implementation of this methodol- ogy, which resulted into a first wireless measurement sys- tem for bowing parameters, the antenna worked as the re-