Despite their many organological and esthetical differences, bagpipes are all played by the movement of the arm on a bag, creating enough pressure to activate the reeds and produce sound. In 2016, an interdisciplinary team of acousticians and an ethnomusicologist within the inter-institutional Geste-Acoustique-Musique project focused on understanding how a bagpiper exerts control on their bag, enhancing our comprehension of the importance of the arm during a musical performance. In this article, we observe what role the arm plays in controlling the instrument, whether a player controls the bag for musical purposes, and whether this influences repertoire and the performance itself. Evidential material consists of acoustical data collected during two experiments in different cultural contexts and with musicians of different levels, together with the statistical and empirical results of an online questionnaire about bagpipe bag techniques. With acoustic measurements, quantitative and qualitative data as well as an ethnomusicological framework, this research offers the first multidimensional and interdisciplinary study of the control of the bagpipe’s bag