The experience of engaging with music through listening, teaching and learning would be impossible without a bodily interface, through which movement and music can be physically produced, experienced and understood. Physical gestures form a central part of the communication established between the teacher-student dyad in the communication of symbolic and functional musical knowledge. Factors such as gesture types (forms and meanings) and their specific outcomes in the teaching and learning processes, have been consistently overlooked in the instrumental music pedagogical context. This thesis prioritises such undervalued topics, focusing its enquiry upon piano teachers' physical hand gestures used to communicate with students during the teaching process. Thus, it incorporates and bridges theoretical frameworks from disciplines including music-psychology, psycholinguistics, gesture studies, gesture-led educational research, imitation and observational motor-learning. Three investigations were carried out. The first two combined qualitative and quantitative approaches - results of which were used in establishing the first known categorisation of piano teachers' gestures. Amongst the most intriguing findings were the relationship between teachers' didactic intent and the forms of gesture they employed, and 'gestural scaffolding' (when teachers adapted particular gestural communicative channels to suit specific student skill levels). In the third investigation an experimental setting was used to observe and evaluate the role of teaching gestures in one-to-one instrumental tuition. Here different gestural teaching and learning conditions yielded multiple levels of learning effectiveness, implying a need for empirical understanding and establishment of gestural performance as a concept that can be applied to enhance learning across specific pedagogical contexts. As well as building a case for future investigations in this research area, this thesis opens a debate within studies of pedagogical practice in instrumental music teaching, whilst contributing more generally to discussions of how the body impacts upon music understanding.