The Role of Smart, Haptic Wearables in the Performance of Mensura

ABSTRACT This article introduces the concept of ‘wearing-in-performance’, the phenomenon of using digital, wearable technologies in musical performance. The research uses ethnographic methods, analysing interviews and statements made by musicians in the rehearsal and performance of Mensura (2022), a work of experimental concert music composed by the author, in order to scrutinise the phenomenological role of such technologies. The paper identifies three phenomena experienced by these musicians, namely connectedness; the meditative reconfiguring of space; and an augmenting of the body. It goes on to conclude that the experience of performing with wearable, haptic technologies is a dynamic gathering of entangled and networked phenomena.


Introduction
This article examines the role of smart, haptic wearables within the performance of experimental concert music.Mensura (2022), composed by the author, utilises the combined Soundbrenner Pulse device-a vibrating, wearable metronome-and app as both controller and quasi-score, to regulate sounds and actions performed by the ensemble.The paper firstly introduces information about the device and composition, subsequently providing both musical and theoretical contexts.The primary discussion is dedicated towards the ethnographic analysis of musicians' experiences whilst rehearsing and performing Mensura.This analysis seeks to provide new insights into the complex and entangled phenomena of performing with wearable technologies.

Soundbrenner Pulse
Soundbrenner specialise in developing wearable tools and software for musicians.The Pulse, is a smart, vibrating metronome designed to be worn on the wrist, waist or leg via straps of varying sizes.Pitched as an alternative to the traditional, sound-based metronome, the Pulse allows a musician to 'feel it [the beat]' (Soundbrenner, n.d.) through distinct vibrations.Soundbrenner claim this haptic engagement with tempo and rhythm, enables the musician to 'free [their] ears for the music'.The shift from auditory cues to vibrations requires a period of 'haptic learning' (Soundbrenner, n.d.) by the user, a transferral of sensorial foci.
The Pulse device can cue numerous, customisable time signatures and emphasise any beat or sub-rhythm within this framework.Additionally, the Pulse can produce nine distinct vibrations varying in strength (weak, medium and strong) and length (short, medium and long).The tempo is adjustable by either tapping the capacitive touchscreen or twisting the outer control wheel, both of which feature flashing LED lights synchronised with the vibrations.
Furthermore, the device can be controlled remotely via the Soundbrenner Metronome app, allowing customisation of tempo, time signature, vibrations and lights.Tempo is similarly adjusted in the app via tapping and wheel interface.Pulse devices connect to the app and one another via Bluetooth.
The regulation of tempo on the app through kinetic actions such as tapping is particularly pertinent to Mensura.According to Pau Senabre, Engineering Lead at Soundbrenner, both Android and iOS apps use 'the same linear regression algorithm to calculate BPM based on time stamps.We queue tap timestamps and estimated BPMs so we can get a regression curve and pinpoint a value' (personal communication, 16 August 2022).The device and software follow the user's tapping whilst the user simultaneously embarks on their haptic learning: the use of the Soundbrenner Pulse and app might therefore be described as an iterative interaction between machine and human.

Mensura (2022)
Mensura (2022), composed by the author, is a musical work for an open ensemble of 3-10 performers using Soundbrenner Pulse devices and apps (via smartphone or tablet).Mensura was commissioned by Cyborg Soloists 1 for amateur music ensemble CoMA Manchester. 2  During my initial experiments with the Pulse, I was interested in the ability to control tempo through the act of tapping.Being an amateur medievalist, I was interested in the parallels between this ability and suggestions that musical tempo in the fifteenth century was measured by tapping an object or singer's shoulder with the hand (DeFord 2015, 51).
Concurrently, given DeFord's claim that units of musical time in the medieval era were related to the human pulse (81), I became fascinated by the notion of respiratory sinus arrhythmia (RSA), in which heart rate and respiration rate affect one another (Vickhoff et al. 2013).Specifically, I was interested in the suggestion that, in the performance of vocal music, RSA can mirror musical structures and result in synchronising heart rates within ensembles (Vickhoff et al. 2013).These two contrasting stimuli provided an imaginative and behavioural framework within which to compose.
In Mensura, each performer measures their heart rate at the neck and taps this pulse into the Soundbrenner app.This tempo is received by a Pulse device worn on the wrist of a separate performer, who performs various breathing and singing exercises according to this given beat.Once they suspect a change in their own heart rate due to these exercises, they measure their pulse and tap this into their own app, which is received by another performer, and so on.Each performer continuously influences the next performer's tempo, who alters the next, until returning to the first performer.The distribution of heart rates and pulses in Mensura might therefore be described as a feedback loop, in which a function of the system's output-in this instance, a performer's BPM-is fed back in as an input via the device.Furthermore, if the act of breathing and singing together does lead to a homogenisation of heart rates, as described above, this would lead to a negative feedback, reducing fluctuations-or the divergence of BPMs-in the output.
In the first section of Mensura, players individually perform three distinct activities according to the tempi received via the Pulse watches (Figure 1).The first is based on the box breathing exercise, a form of yogic deep breathing regularly used to calm and lower the heart rate.The second is based on the Bhastrika, or 'bellows breath', another yogic exercise used to energise the body and increase heart rate.The last activity requires the performer to sing a regular 3/4 rhythm until they coincide with another singer, implying a synchronising of heart rates.Each performer individually cycles through these activities, meaning the tempi received via the watches fluctuate wildly within the ensemble.The result is an intimate network of cardiovascular polyrhythms, regulated by the Soundbrenner devices and app.

Context and Definitions
Before scrutinising the role the Soundbrenner Pulse devices and app play in Mensura, their relationship with the performers and their ability to reconfigure performers' relationships with one another, I outline the varied contexts, both musical and theoretical that the work occupies.Mensura shares aesthetic and methodological affinities with various works of the experimental music tradition.Particular works by composer Charlie Sdraulig, such as close (2018), also employ the performer's breath as a sonic, expressive medium whilst exploring its capacity to regulate musical and social interactions within the performing ensemble.close operates on the edge of perceptibility and, as such, engages with the limitations of the breath and performative body i.e. the varying lung capacity of performers, or the ability of ensemble and audience members to hear such intimate sounds.Additionally, in Alwynne Pritchard's collaborative composition Stamp Club Report 1980 (2018), performers use their voice and breath to mimic an audio score played on sound-blocking headphones.The performer might hear their own contribution but are not made privy to the entire, combined ensemble sound.Pritchard (2021) describes the piece as a series of 'invitations to investigate the breath' and the body, while the juxtaposition of private and public music-making also interrogates socio-musical relationships and behaviours.Mensura invites the performer to listen and respond to their own body and those of others.
However, unlike the above examples, this interaction is regulated through the use of digital, haptic technologies.Whilst the performers of Mensura respond to their bodies, this interaction is communicated by tapping the Soundbrenner app on their smartphones.The performers connect to the ensemble network via this point of interface.Likewise, the performers 'listen' to one another through vibrations received on their Pulse watch, a second point of interface between the body and computer; this is the signal output of the network, translated through performed sounds.
In order to understand the ensemble in Mensura as a communicative, expressive network, I review two further definitions.Musical haptic wearables for performers (MHWPs) (Turchet and Barthet 2019) are a class of devices that employ touch as a medium to improve communications and accessibility for both performers and audience members alike (Turchet, West, and Wanderley 2020).Other studies have shown how such devices can aid the performance and understanding of complex rhythms or sequential movements (Bouwer, Holland, and Dalgleish 2013;Holland, Bouwer, and Hödl 2018).Furthermore, vibrotactile feedback has been used to enhance motor skills, steering the performer's body when learning the violin (Johnson, van der Linden, and Rogers 2010), for instance.However, though such studies use MHWPs to improve coordination and accessibility, they do not explore musical expressivity as a key function of these devices.Whilst Michailidis (2015) investigates the expressive potential of vibrotactile feedback in the domain of interactive electronic performer, their primary aim is to 'express the technology they are using within the compositional process' (141).The resulting practice is about the technology itself.In contrast, Mensura uses MHWPs and vibrotactility to facilitate, rather than improve, communication and interactivity within an ensemble.The Soundbrenner devices are not used for pedagogic purposes, nor to aid accessibility.Rather, MHWPs facilitate expressive interactions between listening and responding performers and their bodies.Mensura cannot be said to be about the Soundbrenner devices, but about human connectivity.
MHWPs are part of the Internet of Musical Things (IoMusT), an emerging field that resides at the intersection of Internet of Things, new interfaces for musical expression and numerous other human-computer paradigms (Turchet et al. 2018).It describes the ensemble of computing devices capable of sensing, acquiring, processing and exchanging data to serve a musical purpose (61995).Whilst the concept describes the 'musical mesh where possibilities of interactions are countless' (61996), the definitions, possibilities and challenges identified are located within a computer science perspective.As such, IoMusT is less concerned with issues of expressivity and musical connectivity (i.e. the interpersonal relations within a performing ensemble).The Internet of Bodies (IoB), however, describes 'the connection of [the] human body to a network' (Khanna, Kapahi, and Gupta 2021, 3).The network in Mensura consists of human performers, their smartphones and Pulse devices, and the various cardiovascular and respiratory cycles that phase in and out of one another.The performers' connection to this network, as described above, is made through interactions with the Soundbrenner hardware and software, interlinked via Bluetooth.But, crucially, these interactions, rather than an exchange of data between 'users', are principally musical, bodily and expressive.Although utilising diverse methodologies, these perspectives provide a vital context through which to understand the function and entanglement of the Soundbrenner Pulse devices in Mensura.

Performer Perspectives
In order to investigate the role of wearable technology in Mensura, the author conducted conversations with multiple performers of the work. 3This approach seeks to interrogate the experiential and expressive effect wearable digital technology has on musical performance.The nature of these conversations is varied and includes discussions held in workshops and rehearsals as well as semi-structured interviews.Whilst these conversations and their analysis are ethnographic in method, the author recognises his dual status as both ethnographer and composer of the musical work in question.Performers' comments may be directly and indirectly influenced by this status.
The performers (henceforth abbreviated to P1, P2, … P5) are derived from two musical ensembles: CoMA Manchester, and a scratch ensemble of students and staff from Royal Holloway, University of London, Music Department.The amateur (or, at least, partially amateur) status of the ensembles lends a particular perspective on the subject.Despite claims that higher-power music technology is becoming more readily available (McPherson 2019, 193), amateur contemporary music ensembles still have limited access to novel devices such as wearables or sensors owing to the finance and digital know-how needed to acquire and explore such technologies.The performers interviewed had no previous experience using the Soundbrenner device, perhaps limiting any presupposed notions of its intended, commercial uses.Their comments and responses to questions might therefore be seen as more immediate, more reflexive, and visceral, to their experiences.
After grouping performers' responses together, I identify three themes: Connectedness; Meditation and Spatiality; and Augmenting the Performing Body.These themes are analysed using ethnographic methods and contextualised with theorems and observations from the wider field of haptic, wearable devices.

Connectedness
Several performers felt that performing Mensura and, more specifically, performing using the Soundbrenner technologies, created a sense of connectedness within the ensemble.P3 firstly recognised that the performers 'weren't connected as an ensemble … just through one person.So that [connection] obviously would have happened through a chain reaction'.The word 'connected' is ambiguous here.On one level, it could refer practically to the Bluetooth connection between one performer's watch and another's app.Yet, it might also relate to the capacity to communicate musically with one another, or even to a more abstract understanding of connectedness, of being integrated and intimate as an ensemble.This latter form of connectedness is 'a significant psychological mechanism' (Kang and Kim 2020, 52) underlying a user's feeling of agency in smart object interactions.Although P3 recognised they were linked to only one other performer, they felt a sense of agency in contributing to this chain reaction.
P3 then expanded on their first comment, comparing the performance to 'an isolation to create a larger thing' and suggested the Soundbrenner devices aided this sense of aggregation.This 'larger thing' might be the musical composition-the musical texture or performative spectacle-or a network as theorised in IoB.Although on a small scale, the simple, sequential Bluetooth connections in Mensura create a ring network, in which each node joins with two other nodes, for the human performer to participate within.
However, another, social connection was perhaps formed before any music-making occurred, both within rehearsals and performances.P4 echoed similar sentiments to those of P3, claiming that 'when we swapped the Soundbrenners [after syncing with the app, before the performance], that helped us become more of an ensemble and to connect us'.In addition to the chain reaction, a sense of connectedness is garnered simply through the communal use and exchange of digital devices.In this instance, the Pulse watches, beyond their status as digital controllers, become symbolic of exchange, and communality.This symbolic function is common to sentimental jewellery such as watches more generally (Silina and Hsu 2018, 4) but also common to communicative, haptic devices, considered the user's 'representative in interactions … , their "go between"' (Shen et al. 2019, 270).The Soundbrenner becomes an agent within this sense of connectedness, participating in a very particular form of communal interaction.
In addition to feeling a sense of connectedness after swapping the watches, P4 added that 'just feeling the other person's pulse on your wrist adds to that'.The nature of the interaction via the Soundbrenner devices is significant here.P4 found the sharing of human heart rates was 'intimate' but, crucially, that this communication was facilitated by a 'mechanical thing … I don't think took away from that'.Of course, a collective musical performance of any type might facilitate such sentiments (Magnusson 2021, 177).In particular, those that utilise the voice invoke the 'intimate relationship' (178) with our self and body.Yet, P4 acknowledges the specific role of the Soundbrenner device in facilitating this intimacy.As suggested by Shen et al. (2019, 271), the representation of another's body-here, their heart rate-through a haptic, communicative device might give 'an illusion of physical proximity'.This tactile interaction is a 'fundamental aspect of interpersonal communication' through which 'the presence of the other person is thus made tangible' (Brave and Dahley 1997, 1).
Furthermore, we might view the Soundbrenner's representation of the human heartbeat as an anthropomorphising of the watch.The attribution of human status and behaviours to inanimate entities promotes feelings of 'connectedness' as 'users experience a strong sense of "another being" independent from themselves' (Kang and Kim 2020, 48).This other being is the Soundbrenner watch, with its uncanny pulse, and the performer whose heart rate is represented; conjoined agents with separate loci of agency within the micro-network of interaction.
To summarise, for the performers of Mensura, the Soundbrenner Pulse and app facilitated a sense of connectedness-both structural and symbolic-during rehearsal and performance.The use of a haptic, communicative wearable to depict biological processes lends the Pulse an anthropomorphic status.The resulting multi-agent network comprises a meshing of the human and the machine; an intimate entanglement of connections.

Meditation and Spatiality
One performer described the meditative qualities of Mensura.More specifically, P1 compared measuring their heart rate and tapping this into the app in the first workshop to getting into a 'trance'.Over a sustained period of time, they established a rhythm of dividing attention between measuring and tapping, of receiving and sending kinetic signals.P1 went further to compare this dividing of attention, of discounting one signal-the watch pulse on the wrist-whilst prioritising the other-the heart rate at the fingertips-to 'letting sounds wash over you whilst you're meditating'.P1's choice of metaphor here is interesting.Feasibly, they may have unconsciously derived the image of washing sounds from the breathing exercises and the contrapuntal textures these create.However, P1 regularly engages in meditative activities such as yoga outside of their musical practice.They may therefore have a greater sensitivity towards and inclination to investigate such states (Walsh and Shapiro 2006, 235) and be more likely to make such comparisons.
The exercises performers are asked to carry out in Mensura (Figure 1) are informed directly by yogic practices, perhaps evoking meditation qualities.Consider the role of breath, a 'key element of meditation' (Hao et al. 2017, 2), as both a sonic material and mechanism through which to alter the musical tempo, but also as a bodily site to focus attention (Heeter et al. 2017, 315).
If the foregrounding of the breath in Mensura creates an abstract link with meditative practices, it is furthermore performatively grounded and processed using the Soundbrenner app and device.When the performer measures their heart rate, their fingers touching their neck, they purposefully direct their bodily attention.In meditative practices, this is known as 'interoceptive' awareness (Farb et al. 2015).They then attempt to replicate this pulse by tapping into the app, transferring one haptic perception into a performative gesture.We might compare this transference to the 'process of receiving, accessing and appraising internal bodily signals' (1).
Furthermore, several performers expressed a sense of disembodiment or dislocation.P3 recounted that 'feeling it [the watch pulse] took you out of the space and … put you in … I wasn't looking around or feeling the space, it was just contained' [emphasis in original].Seemingly, P3 felt an abstract sense of introversion or interiority when using the Soundbrenner Pulse.Conversely, P4 and P5 experienced a feeling of exteriority on account of the minimalist watch-app apparatus, i.e. the absence of the score in performance and directing visual attention away from the phone screen.Whilst P4 felt the ensemble could 'resonate more … out in the open … [and] fill the space' because of this configuration, P5 felt they could 'sing out into the space … just there in the space … up and open' [emphasis original].Whether relating to interiority or exteriority, performers clearly felt that using the Soundbrenner technologies led to a sense of dislocation and reconfigured spatiality.
This modified spatiality creates another, more subtle, link to meditative practices.Within such practices, notions of 'inward and interiority are not metaphors … but refer to the spatial direction of one's awareness, or self-contact' (Blackstone 2008, 448).The attention of performers, simultaneously directed through and towards the body, the space and the Soundbrenner technologies might be described as exhibiting qualities of contemplative practice, in which 'interoceptive signals are integrated into a complex representation of self and the world beyond' (Farb et al. 2015, 4).

Augmenting the Performing Body
All five of the performers interviewed experienced some form of confusion between the pulse at the neck (the heart rate) and the pulse on the wrist (the watch-another's heart rate).This confusion occurred at both a haptic and mental level.Both P3 and P4 explicitly recall a difficulty in discerning what was felt on the wrist and in the hand, whilst P4 also acknowledged the need to 'mentally differentiate' between these.Whilst the use of the Soundbrenner devices in Mensura deviates from their intended use, this confusion possibly points to the 'haptic learning' mentioned above, a process of shifting focus from sound and internalising the haptic (Pau Senabre, personal communication, 16 August 2022).The confusion outlined by our performers-a blurring of boundaries between the felt and thought, a haziness between body and wearable-leads to other entangled phenomena.
As an example, one performer found the confusion experienced between the two separate pulses felt at the neck and wrist led to an altered sense of her own body.P2 confided, I'm finding it really hard not to [… } make it into a rhythm […] between my pulse and [the watch pulse][…] And it's making me feel like my heartbeat is literally sometimes being long.
For P2, the two pulses combine to form a single cross-rhythm, displacing, even, her interpretation of her heart rate.This blurring of boundaries, in which the wearable is subsumed into the body, or the other way around, is an example of Ryan and Salter's technologically 'exaggerated body' (2003, 89), whereby the physical boundaries of the body are expanded using sensor-integrated garments.By drawing attention to bodily actions, the pulse from the watch caricatures the heart rate.Alternatively, we might alter the loci of agency within P2's experience, and suggest that her heart rate becomes the watch pulse.
Notions of the cyborg (Haraway 2006) appear in other performers' experiences, who, throughout rehearsal and performance process, began to feel as if the Soundbrenner watch were a part of, or extension to, their own body.P4 claims, 'It [the watch] did become an extension of me.I was more familiar with how to use it, but also what to expect, even response times'.The augmentation of the performing body in music instrumental practice is well documented (De Souza 2017;Le Guin 2006).However, the wearable nature of the Pulse watch is pertinent here.Beilharz et al. (2010, 323) claim that a wearable 'crosses over the territories of … expression, individuality and intimacy of a kind of body extension'.P4's growing familiarity with the watch's behaviours, and responding to this, aids this sense of extension.Nugroho and Beilharz go as far as to claim that this enhancing of the body is the very purpose of wearable expressions (2010,329).This crossing of territories, of familiarity and responsiveness with the wearable, alters the Soundbrenner's status from controller to agent, able to inform and shape performers' gestures and experiences.
Furthermore, the haptic function of the watches specifically led to a sense of bodily augmentation.P3 not only agreed the watch began to feel like part of them but also that 'the pulse was in my wrist … instead of this thing on my wrist' [emphasis original] and that, through 'feeling it, it became part of us' [emphasis original].This not only recalls P2's experiences but goes further to specifically suggest a metaphorical subsumption of the watch into the body.This conception counters Nugroho and Beilharz's 'Cyborg Notion', in which 'the human body is seen as increased and augmented by its attachment to technology ' (2010, 329).This goes beyond simply extending or augmenting the body.Such readings fail to recognise the miring of humans in technology (Tahiroğlu and Magnusson 2021, 120).Rather, this is a thingly becoming in the Heiderggerian sense (1971,179).The body, also a thing (Ingold 2013, 94), becomes the wearable.Similarly, 'the machine is not external to the worker' (Ingold 2002, 305), but becomes the performer.
Wearing-Haptics-in-Performance: A Gathering Three distinct themes, arising from conversations about the performance of digital wearables in Mensura are identified: connectedness; a meditative reconfiguring of space; and an augmenting of the thingly body in its becoming.While these themes are identified and discussed above, they represent phenomena that feed into and out of one another in complex and entangled ways.On the one hand, one might lead to or aid the sense of another.For instance, P4 suggests that because of the sense of connectedness garnered by the watches, it was easier for the ensemble to fill a space.On the other hand, one phenomenon might occur in spite of another; consider the supposed disparity between a performer feeling 'out' of a space-of being bodily displaced-and simultaneously having their attention directed into the body, its limits and boundaries.Akin to the transferral of pulses between performers via the watch and app, these phenomena entangle with one another in an intricate, iterative mesh.
The term wearing-haptics-in-performance is coined to describe this ensuing counterpoint-an interweaving flux augmented embodiment; of attentiveness; and of leading and being led (Ingold 2013, 101)-and constitutes the experience of performing wearable, haptic technologies in Mensura.This multimodal experiential system is a 'dynamic compliance' (Ryan and Salter 2003, 89), in which multiple phenomena might dynamically feed into and out of one another.In Mensura, the performance of wearable digital technology is dynamic, entangled and networked.Wearing-haptics-in-performance is 'a coming together of materials in movement' (Ingold 2013, 85), a 'gathering' (85) of the body, with other human, nonhuman and imagined bodies.

Conclusion
This article introduces the notion of wearing-in-performance, the phenomena of performing with wearable, digital technologies in Mensura, a work of experimental contemporary music.Developed as a result of ethnographic analysis of musicians' interviews and statements during rehearsals and performances, the described phenomena are limited to this composition and technological apparatus.It is hoped practitioners and researchers engaged in similar work might find it useful.The purpose is not to confine the articulation of such performative scenarios, but rather to open up discussions relating to MHWPs; and to offer experiential terms and concepts.
Further research is needed on the use of wearable technologies in musical performance, especially comparative analysis of separate and contrasting musical works.Furthermore, phenomenological examination of audiences spectating such works might provide complimentary lenses through which to scrutinise the topic.

Notes
1. Cyborg Soloists is a UKRI-funded Future Leaders Fellowship led by Dr Zubin Kanga at Royal Holloway, University of London.2. CoMA Manchester, directed by composer Ellen Sargen, is a sub-group of the charity Contemporary Music for All (CoMA).3. Ethical approval was granted via the Royal Holloway self-certification procedure, 03/08/ 2021.

Figure 1 .
Figure 1.Excerpts from Mensura score, demonstrating the breathing and singing exercises.