**1. Introduction**

While musicians are performing on stage or in the studio, monitoring on headphones interferes with their instrument embodiment, the auditory feedback of their sound within room acoustics, and their interactions with other musicians. Indeed, wearable monitoring devices disturb the physical and technical ease that performers have acquired over a long, multi-sensory process to play their instruments or conduct ensembles at their best level. By covering their ears, headphones also jeopardize musicians' ability to control the parameters of their sound production. For instance, singers "suffer the most from the dislocation of sound that headphones engender […] because the sound is produced in their bodies, resonating in the chest cavity and sinuses" [1]. As another example, the absence of direct auditory feedback compromises "the production of high-quality trumpet tone [that] is achieved by a combination of the correct vocal tract position, the lip-reed mechanism, and the player's breath control" [2]. Moreover, headphone monitoring obstructs collective soundscapes and established ways of listening and playing music together. To mitigate these challenges, performers sometimes remove one earcup [1] to attenuate their feeling of exclusion from the acoustic environment or to compensate for the lack of externalized sources that wearable monitoring devices as opposed to onstage speaker monitors induce [3]. In this chapter, we examine orchestra conductors' and music improvisers' experiences with wearable monitoring devices, and we discuss three binaural technology solutions that overcome stereo headphone monitoring challenges for a range of professional performance contexts.

Headphone monitoring was introduced in recording studios where it was necessary to isolate sound sources and synchronize performances on cue tracks while enabling musicians to hear themselves and others. Whereas this technology offers flexibility and creative possibilities such as overdubbing on previously recorded takes, it calls for the use of visual cues through windows and red lights, and for the setup of talk-forward and talkback microphones that may expose musicians to the others' comments on their performances. In such a technological environment for music creation, sound engineers control both the quality of headphone mixes and the communication system in the studio. Williams highlighted how the setup of the communication system increases stress and may result in tensions between musicians and engineers during recording sessions [1]. Also, adding headphone monitoring as yet another layer of engineers' sound control may worsen experiences of gendering and microaggressions in the commercial recording studio [4]. Therefore, although "the number of available headphone mixes becomes a status marker reflecting the professional standing of the studio among competing facilities" [1], using a high number of headphone mixes may negatively impact the production workflow and the social climate of the workplace. Our approach consists of adapting technologies to specific performance contexts to enhance musicians' immersion in their artistic tasks, and thus reduce stress and other adverse sociopsychological effects of headphone monitoring.

The audio content of monitoring systems influences all aspects of musicians' performances, in positive and negative ways. For instance, balancing harmonic versus rhythmic sections in a singer's or a melodic instrumentalist's monitoring mix impacts their comfort in finding their best tuning, rhythmic placement, and dynamics. Furthermore, signal processing like equalization, dynamic range compression, delays, and reverberation is commonly used to facilitate ensemble cohesion. As an example, boosting the attack of the kick drum in a bassist's monitoring mix can enhance the groove of a band. Also, a study showed that monitoring different reverberation lengths of room acoustics affects orchestra conductors' tempo, timbre, and appreciation of the performance quality when listening to recorded takes [5]. Findings from a PhD thesis about live engineering on Broadway underline how engineers are responsible for "sonic colors" that represent "the unique resonant characteristics of sound sources associated with music-making, but also to invoke "color" as a broader metaphor for social difference and identity" [6]. From this perspective, both the sound capture system and mixing approach of monitoring systems must meet the cultural expectations and genre conventions of specific performance contexts. For each of our three binaural solutions, we detail how we designed the monitoring technology, the sound capture system, and the mixing approach to satisfy the requirements of specific performance contexts.

Our interdisciplinary team of four researchers who are also experienced sound engineers and music performers aim at examining the following research questions: *Binaural Headphone Monitoring to Enhance Musicians' Immersion in Performance DOI: http://dx.doi.org/10.5772/intechopen.104845*


Before we present a fresh perspective on the methods and results of a series of three studies that were published in the proceedings of *Audio Engineering Society Conventions* [7–9], we highlight previous research on delivering synchronization auditory cues to performers; augmented and mixed reality audio applications; and binaural music production that informed our solution designs. Then, we discuss the methods and outcomes of two online surveys about orchestra conductors' and improvisers' experiences when monitoring through headphones. The survey findings serve as a basis to support the design of eight case studies that aimed to compare binaural versus stereo headphones in recording or rehearsal situations.

Because musicians rely on the auditory cues that their monitoring systems convey to elaborate their performance process, comparing the influence of binaural versus stereo monitoring on musicians' performances requires researchers to design "ecologically valid" experimental protocols and technologies that address creative cognition [10, 11]. Hence, we carried out our eight case studies in real-life performance situations.

With experienced musicians, to test three binaural monitoring solutions that we designed to meet the esthetic and cultural context of three distinct performance situations. Finally, we provide ideas for future research with audio augmented and mixed reality applications to facilitate musicians' immersion in the performance.
