Musical haptics for the listener, Part I: tactile music enhancement systems for hearing and DHH users

In the past decade there has been an increasing attention towards the field of musical haptics for the listener, which concerns the creation and evaluation of systems conceived for conveying or augmenting music signals through the sense of touch. The primary purposes of these systems are to enrich the musical experience of hearing listeners and to enhance music perception for listeners with hearing loss. This paper (Part I of a two-part review) surveys the state of the art in musical haptics systems for listeners, with a focus on technologies, system architectures, and design strategies. We introduce a taxonomy that classifies existing systems according to their application domains, accessibility focus, actuator technologies, haptic rendering approaches, form factors, and deployment contexts, and we apply it to a systematically collected body of literature. Building on this analysis, we describe the core components of musical haptics systems and examine trends in wearability and connectivity, and the needed shift from laboratory prototypes toward live and ecologically-valid scenarios. We further discuss technical challenges related to offline and real-time processing, latency, synchronization, and the deployment of machine-learning techniques on embedded hardware. Part II of this review will complement the technical perspective presented here with a survey of the perceptual, emotional, and behavioral effects of musical haptics systems on both hearing and Deaf and Hard-of Hearing users.