Performance Practice
of Electroacoustic Music

Horacio Vaggione

Shifting Mirrors


Shifting Mirrors was created in 2016 at the Centro Mexicano para la Música y las Artes Sonoras (CMMAS). Its first performance took place at the Visiones Sonoras Festival in Morelia, Mexico. The piece was developed in close cooperation between the composer and saxophonist Pedro Bittencourt, to whom it is dedicated.

The title refers to composition techniques resulting from Vaggione’s concept of multi-scalar and multi-local objects (for an introduction to Vaggione’s theoretical thought see e.g. [Vaggione 2010]). In this case, these objects are recorded and sometimes slightly modified saxophone sounds, which enter a complex system of variations. [Document 2, p. 1] In most cases the original saxophone sounds can be recognised.

“The title Shifting Mirrors could be translated as “Espejos mutantes”: the same kind of material is heard from different perspectives, like in those mirrors in which you appear bigger or slimmer, etc.” [Vaggione, 2018]

The process of the piece’s genesis is reflected in two different versions, a “participative” and a “standard” one. [Document 1, p. 1–2] In an interview with Germán Toro Pérez [Interview, 2:50 – 3:30], Vaggione talks about the point of departure: In his PhD thesis, Bittencourt had called for a “interprétation participative” [Bittencourt 2015, s. also Document 1, p. 1] involving the performer in the creation of a piece. Vaggione then proposed to Bittencourt a composition that would enable the performer to become actively involved in the creation of sounds. [Interview, 4:08 – 6:12].

Vaggione created an electronic, visual and aural “score” (a Pro Tools session) with 32 audio tracks containing a number of sound objects derived from electronically processed saxophone sound bits with different playing techniques which Bittencourt had prepared. They include various types of slaps, key and air sounds, flatterzunge, bisbigliando and multiphonics. The session would then “[…] [serve] as a guide for the instrumentalist, who must follow it strictly and adapt his intervention to the composed sound structures.” [Document 2, p. 1] Although given some discretion with respect to the combination of sound objects, the performer would thus respect the pitch structure, the sound typologies and the playing techniques of the sound files:

“Silences, intensities, durations and pitches must be strictly respected (à la lettre), with no exception, to keep the formal features (temporal, rhythmic, sonic) of the piece.” [Document 2, p. 1]

While the piece’s macro structure is wholly determined by the composer, the performer can intervene on the meso and micro levels. There is in this sense no improvisation, but there should result an interaction between composer and performer based on the sound files:

“Ce n’est donc pas une improvisation qui est visée ici, mais une collaboration de l’interprète sur la base stricte de ce qui est composé.” [Document 1, p.1].

“The aim here is therefore not an improvisation, but a collaboration of the interpreter on the strict basis of what is composed.” [Document 1, p.1].

Thus, a given instrumental part is one of multiple possible “readings” through the 32 files. These are conceived both as the support for the electronic part and as a fixed but open visual and aural score for the saxophonist.

“Il s’agit donc d’un va-et-vient entre le visuel et le sonore, mais où le sonore (et le temporel en général) a toujours le caractère de référence, à laquelle l’instrumentiste doit se plier.” [Document 3, p.1]

“It is therefore a back and forth between the visual and the sound, but in which the sound (and the tempo in general) always acts as a reference to which the instrumentalist must bend.” [Document 3, p. 1]

Vaggione further points out the relation between Bittencourt’s concept of “interprétation participative” and his own earlier concept of “écoute opératoire”. While “interprétation participative” calls for performers to explore their margin of interpretative freedom within the piece’s micro structure, the concept of “écoute opératoire” implies that listeners, as well, have a margin of action:

“J’irai même jusqu’à dire qu’un acte d’écoute musicale en tout cas une ‘écoute opératoire’, détaillée, et pas seulement ‘immersive’, purement globale, comporte la possibilité de focaliser notre attention de façon variable.” [Vaggione 2010, p. 55]

“I would even go so far as to say that an act of musical listening, in any case, a detailed ‘operative listening’ and not just a purely global ‘immersive’ involves the possibility of focusing our attention in a variable manner.” [Vaggione 2010, p. 55]

This reflects a main formal feature of Vaggione’s electronic music. It consists of multiple sound layers built out of single events in different time scales that merge into textural streams or emerge as figures and singularities, depending on the local musical context and on the listener’s focus of attention. This multiplicity results in fixed but open forms, as it is the case in his electronic composition 24 Variations (2001):

“Perhaps it is precisely due to the grey area between distinctive figure and obscure texture that there are different possibilities to understand morphological aspects of the piece in listening. There is a multitude of formal relationships that can arise or shift and rearrange themselves depending on the focus of attention. By oversupplying the listener’s perception, the piece makes a single interpretation impossible.”
[Mouritzen & Toro Pérez 2014, p. 193, about 24 Variations]

The second, “standard” version of Shifting Mirrors was elaborated in view of the difficulties other performers might have in creating their own versions. Vaggione thus worked out a standardised version, precisely notating playing techniques, pitch structure and rhythm based on the sounds contained in the sound file:

“Afin de pouvoir faire jouer la pièce par d’autres interprètes, sans les faire passer par la phase d’expérimentation participative, j’ai réalisé par la suite une version « standard » en notation conventionnelle.” [Document 1, p. 2]

“In order to be able to have the piece played by other performers without having them go through the participatory experimentation phase, I subsequently produced a ‘standard’ version in conventional notation.” [Document 1, p. 1]

In this notation Vaggione uses precise coordination points marked in seconds, facilitating synchronisation between the performer and the electronic part. Vaggione asserts, however, that this second version is merely one of many possible solutions to be found based on the fixed sound files. [Interview, 25:15 – 25:43]

The electronic part features a characteristic spatial structuring also found in other Vaggione pieces. The 32 tracks are mixed down to three stereo pairs. These are played through loudspeaker pairs symmetrically disposed along an arch in the front part of the venue with the performer in the centre. The three stereo pairs bring sequences or their variations in parallel with slight time delays intended to be heard as a “‛prismatic’ elaboration” [Document 2, p.1], a spatialisation technique Vaggione calls “de-correlation”. [Interview, 35:45 – 36:53]

The piece consists of eleven sections discernible by their specific density, dynamics and sound characteristics and in most cases by pauses marking the end or beginning of a section. The silences become increasingly noticeable. The initially continuous stream becomes fragmentary and finally dissolves into single multi-layered figures at the end of the piece.

In Shifting Mirrors the relationship between soloist and electronics traditionally observed in mixed pieces shifts towards a specific kind of “liveness”; the main challenge for the performers is to generate a situation where the saxophonist listens to, recreates and adapts to the material present in the electronic part, reflecting its temporal and morphologic structure and aiming to integrate into it as a further sound layer. Thus, both parts form a multi-stream body of sound, its structure of shifting layers being reinforced by the spatial disposition.


1) Performance Materials:

a) Score: Composer’s edition, 2016
Source: Horacio Vaggione
Format: pdf

The score only includes the notation of the saxophone part. There are explanations referring to the symbols used for the various playing techniques. There is no information on the electronic part, except time indications in seconds used for synchronising important sound events between the acoustical and electronic parts.

b) electronic part
Source: Horacio Vaggione
Date: 7 October 2016
Format: Wave 44.1 kHz/24b
Duration: 10:01
Remarks:Containing folder labelled “Shifting Mirrors version 6 pistes”

Horacio-SHiftMirrors_sess 3 – 1-2.wav
Horacio-SHiftMirrors_sess 3 – 3-4.wav
Horacio-SHiftMirrors_sess 3 – 5-6.wav

2) Other materials

The following documents received from the composer contain extensive information on the genesis and performance:

Horacio Vaggione, SHIFTING MIRRORS, pour saxophone alto et 32 pistes numériques, note 3
Date: undated
Remarks: French, two pages, quoted as Document 1. It refers mainly to the participative version.
File: Shifting Mirrors, note 3.pdf

Horacio Vaggione, SHIFTING MIRRORS (ESPEJOS MUTANTES) for alto sax and electronics
Date: November 2016
Remarks: English, two pages, quoted as Document 2. It refers to the participative version.
File: SHIFTING/ENGLISH long 3.pdf

Horacio Vaggione, Shifting Mirrors (2016) pour saxophone alto et électronique, Indications partition normale
Date: Undated
Remarks: French, 1 page, quoted as Document 3. It refers to standard version with 8-channel electronic part.
File: Indications sur Shifting Mirrors 2 – partition normale.pdf


Auctorial Instructions

1) Score:

The playing techniques (alto saxophone) are explained in the text itself. Besides tempo (crotchet = 112) and meter (4/4), the score includes time stamps for synchronisation with the tape:

Fig. I
Fig. I. Shifting Mirrors, bars 33-34


Bar 161, 162: Indications for multiphonics are unclear, the electronic part introduces multiphonics starting only at bar 163.

Bar 143 has the indication “silence”, however, the rests in the tape part start only at bar 144.

2) Other sources

A. Standard version

Document 3 provides information about the setup and playing techniques used in the standard version. The speakers are to be placed behind the player in a semicircle. However, the document refers to a previous version of the piece realised using an 8-channel version of the electronic part.
During the second project workshop at ZHdK in June 2019 the composer gave precise instructions on how to set up the loudspeakers for the six-channel version of the electronic part (see Performance report below).

Regarding tempo and synchronisation in the score, Vaggione gives the following explanations in Document 3:

“l’indication noire 100 est approximative, car il faut se synchroniser avec l’électronique. Pour un repérage plus sûr, suivre les indications chronométriques inscrites sur les portées”
“The tempo indication 100 is approximate because it must be synchronised with the electronics. For a safer location, follow the chronometric indications written on the staves.”

Nevertheless, in many places the de-correlation implies small shifts between both parts that have to be respected:

“Ces décalages sont voulus, car ils forment la texture granulaire – spatiale de l’oeuvre. C’est pour cela qu’elle s’intitule ‘Shifting Mirrors’ (Miroirs décorrélés).”

“These offsets are wanted because they form the granular – spatial texture of the work. That’s why it’s called ‘Shifting Mirrors’”

Pitch and intonation
Similarly, the intonation has to correspond to the electronic part [cf. Document 3]:

“Les hauteurs sont à respecter telles qu’elles sont écrites, car elles se trouvent en correspondance avec le plan harmonique de l’œuvre, tel qu’il est affirmé dans la partie électronique.”

“The pitches must be respected as they are written, because they correspond to the harmonic plane of the work, as stated in the electronic part.”

This is also important for the intonation, speed and colour of the trills (e.g. bar 46 ff), as well as for the choice of multiphonics (e.g. bar 163 ff).

Alterations are valid for the whole measure.

Playing techniques
Vaggione refers to these as “generic” techniques that can be realised according to the performer’s preferences, but

“toujours en tenant compte du contexte créé par la partie électronique. Le jeu ‘coup de langue’, cependant, doit s’appliquer toujours, en suivant celui de la partie électronique.” [Document 3]

“always taking into account the context created by the electronic part. The ‘slap tongue’ technique, however, must always be applied following that in the electronic part” [Document 3]

The composer insists on the necessity to study the electronic part thoroughly – just as the score – in order to understand the role of the soloist.

B. Participative version

In Document 2 the composer describes a different speaker setup using a minimum of four loudspeakers, allowing for larger speaker arrays that can also be set up around the whole hall. For the Festival Visiones Sonoras (Morelia, Mexico, 7 October 2016) and the Biennale of Electroacoustic Music of São Paulo, Brazil (16 October 2016), the sound projection setup consisted of an ensemble of 60 loudspeakers.

Vaggione prescribes the use of a screen on stage to display the screenshots of the Pro Tools session and a chronometer for visual synchronisation.

Instrumental part
In Document 2 Vaggione also describes the approach to the playing techniques used by Pedro Bittencourt, as denoted in the screen shots. He also points out a way to find a “trajectory” through the 32 files: The player

“ … can “jump” from one line to another (this being one of the ‘degrees of freedom’ which he can use), but always respecting the metric and sonic features inscribed in the digital support.”

He continues:
“New specific trajectories can be signalised (notated) by the instrumentalist, adding new signs (lines, arrows, words) to the support, and eventually indications of pitch; duration and dynamics; these additions can act as memory cues.”

Performance report

The concert took place on 27 June 2019 at ZHdK (Toni Areal, Zürich) in the main concert hall (GKS 3) with Joan Jordi Oliver, saxophone, and Leandro Gianini, sound engineer and sound projection. The performance was based on the written, standard instrumental part and the six-channel electronic part provided by the composer.

Loudspeaker setting and routing for the electronic part
For the projection of the tape six Kling & Freitag Gravis 15 were placed in a semicircle with the soloist playing in the middle. within the early rehearsal phase pairs 3-4 and 5-6 were placed on the sides surrounding the audience. The composer corrected this disposition and asked for a more fontal and thus compact disposition along a flat arch not surrounding the audience.

The six sound files are organised in three stereo pairs and routed as shown below.

Fig. II
Fig. II. Speaker setup for Shifting Mirrors

For amplification of the saxophone, a DPA 4099 was mounted on the instrument and a Schoeps MK4 on a stand to the right of the player in order to better capture the key sounds. The signals were processed with dynamic equalisation, compression and some saturation. The processing as well as live volume adjustment were essential in order to obtain the required closeness to the tape sound. Some soft playing techniques had to be manually reinforced, especially the key klicks (c.f. score, “clés”).

The processed signals were then routed to the speakers behind the player. Two speakers (L-Acoustics 8XT) in front of the player were added to obtain a better sense of natural localisation.

Monitoring and synchronisation
To display the score and help the player to keep in sync with the tape the Polytempo Network software developed at ICST was used (c.f., providing a visual metronome and displaying the score according to the elapsed tape time.
Due to the de-correlation between similar sound layers it is not always clear how the instrumental part should be synchronised with them. While the score is very precise and detailed and includes time stamps for synchronisation, it is important to extensively analyse and practice with the tape in order to find suitable solutions.

Rehearsing process
When first receiving the standard score from the composer, the performance team was not aware of the underlying concept of “collaborative interpretation” explained above. Joan Oliver first learned the text precisely and based on a conventional understanding of the required playing techniques. [see report below] The exchange both with Horacio Vaggione and Pedro Bittencourt then clarified the required approach. Accordingly, even the standard text has to be understood as a framework to be complemented by the electronic part, which, as stated above, was also conceived as a sounding score. It is therefore necessary to study the tape thoroughly in order to match the specific playing techniques, the articulation and the sound of the original performer.

Further performances
This team had the opportunity to perform the piece again at the same venue shortly after the first performance. For this second performance, it was decided to take into account the movements of the player during the performance. The Schoeps MK4 was replaced with a second DPA 4099 fixed on the instrument and pointing to the keys. The loudspeaker setup was very similar to that used in the first performance. However, a narrower setup leaving less space between the speakers was used, resulting in a more frontal and compact sound.
This approach allows for the soloist to maintain closer contact also with those layers of the tape routed to the more remote speakers. From a listener’s perspective, the differentiation of the three layers may be less obvious; indeed, the piece may sound more powerful, but also less transparent. In general, stronger amplification of the soloist was necessary to avoid the electronics drowning out the live saxophone.
Considering the liberty taken by the composer in the different live setups of the participative version of this piece, it would seem appropriate to consider some experimentation with the speaker placement also for the scored version. In fact, it was observed that even small changes in the distance between speakers would affect the perceived result for the listener and the soloist considerably.

Fig. III
Fig. III. Speaker setup for the second performance.

Remarks by Joan Oliver

The process of learning, rehearsing and understanding Shifting Mirrors has introduced a series of challenges rarely encountered in the saxophone repertoire. At the very first stage of the learning process, we were not aware of the “collaborative interpretation” concept behind the piece, a key idea that would not only shape the composition process, but would completely redefine the performers’ task in the interpretation of the work, their role in the interaction with the electronic sounds and their understanding of the multiple interpretation possibilities that Shifting Mirrors could offer.
A finished score, written in conventional notation and representing quite standard extended playing techniques was given to us together with the electronic part, organised in three stereo files. The habits of a trained performer would guide the learning process when facing a score with such detailed information. Rhythmical motives, precise accentuation, different articulation possibilities, combination of playing techniques and a rich harmonic spectrum (with the extensive use of quarter tones) make for a highly complex and technically demanding score. As this was initially the only source presented to us, I, without knowing that this document was only a single result of endless other possible readings of the piece, assumed that respecting the detailed text would be essential in order to make effective the interaction between my written part and the composed electronic sounds.
Early into the rehearsal process, a number of questions, contradictions and even impossibilities came up, which we often discussed with the whole team. Some had to do with synchronisation issues with the electronic part, as we were asking ourselves if the precise rhythm notated in the score was meant to generate a de-correlation with the pre-recorded saxophone, or if in certain passages of the piece, I should try to make my reading more flexible in order to achieve a more evident connection with the fixed electronic part.
Other problems had to do with the impossibility of performing certain passages of the score, mostly because of the limitations in speed using slap tongue technique or because of a determinate succession of quarter tones. In addition, it took some time for me to assimilate the desired sound of certain techniques, especially the ones with air sounds or the different sound qualities of the slap tonguing. This problematic is quite common in New Music and has to do with the problem of precisely notating the desired sound result of certain techniques. In the case of Shifting Mirrors, it was essential to understand that the written saxophone part would always take up the sounds introduced in the electronic media, meaning that a single way to notate a technique (for example the coup de languequasi slap or the air tk, both very present throughout the score) would allow the performer to flexibly vary the colour and the quality of a certain technique according to their physical abilities (for example, varying the colour of articulation of the slap tongue helps the performer to maintain regularity and precision during the passages with longer repetitions) and, most importantly, according to what is constantly being heard in the electronic part.
Several conversations with both Horacio Vaggione and Pedro Bittencourt shed light on what the piece really was intended to be, how it had been conceived and how a performer should in fact approach its interpretation. We got access to several additional documents that, in my opinion, should be an integral part of the documentation given to the performer together with the score. We discovered the original idea of the visual and aural score, the method preferred by Pedro Bittencourt, the first performer of the work. These discoveries made me shift my focus from precision and absolute respect for the written score to a more flexible interpretation of the notation, of the written extended techniques and, at a few specific moments, even of the rhythmical gestures. Most importantly, they made me understand the necessity of constantly listening to and being in a dialogue with the multiple saxophonists inside the speakers. We decided to keep performing the standard version of the score instead of switching to the visual score, since much of the work had already been done and we got to elaborate a very detailed version in this format. But the renewed and broader perspective we acquired after the numerous rehearsals and the discussions with Vaggione and Bittencourt made us understand the real function of the score, and therefore also the role of the performer and the sound universe of Shifting Mirrors.
At this stage of the work, after having performed the piece on several occasions and having recorded it, one can better understand the nature of Shifting Mirrors as a piece with many different possible perspectives. It should not be understood as a more traditional “solo performer with electronics” piece where the instrumentalist defines most of the sound materials and where the role of the soloist dominates the electronic part, in many cases just a duplication or extension of the functions and capacities of the performer.
In Shifting Mirrors, the activity of the performer inside the piece constitutes merely an additional perspective on a very complex texture of sounds where individuality melts into a cluster of simultaneous voices. A single gesture by the performer will never be presented isolated but replicated multiple times with slight temporal and colour variations in the electronic part, which will constantly confuse the perception of what is being produced in real time and what was already pre-recorded. In many instances, the performer doesn’t happen to be the main source of generation of sound materials, as this function constantly shifts between the electronics and the acoustic instrument. These conditions put the performer in a very particular and quite uncommon situation where his or her role is not the most prominent part of the piece, but just a complementary musical line equally important as the many, many simultaneous lines presented in the electronic part.
From my point of view, and as Vaggione would sometimes state himself, the electronic part of Shifting Mirrors could already be a finished piece of music. Any variations – adding or taking out some of the tracks, completely changing the solo part, etc. – would still not much alter the nature of the piece. To me, the most important function of having a performer on stage playing the piece (or with the piece!) is precisely to create this situation of confusion, a perceptual game where perspectives constantly change and where the dramaturgical possibilities of illusion (the false idea of the electronics as an extension of the performer, since a human body on stage will always remain the focus of our attention) are a compositional strategy.

Selected Bibliography

Bittencourt, Pedro (2015): Interpretation musicale participative – La médiation d’un saxophoniste dans l’articulation des compositions mixtes contemporaines. PhD thesis (unpublished), Université Paris 8 – Vincennes – Saint-Denis.

Mouritzen, Kenn &Toro Pérez, Germán (2017): Über die Mannigfaltigkeit der Rinde. “24 Variations” von Horacio Vaggione im Kontext einer wahrnehmungsinformierten Analyse elektroakustischer Musik. In: Lang, Benjamin (ed.): Lost in Contemporary Music? Regensburg: Con Brio, pp. 173–227.

Vaggione, Horacio (2019): Interview. Conducted by Germán Toro Pérez, 27 June 2019. [quoted as Interview]

Vaggione, Horacio (2018): Email to Germán Toro Pérez, 15 March 2018

Vaggione, Horacio (2016): Shifting Mirrors (Espejos Mutantes) for alto sax and electronics (pdf, dated two pages) [quoted as Document 2]

Vaggione, Horacio (2010): Représentations musicales numériques: temporalités, objets, contexts. In: Soulez, Antonia & Vaggione, Horacio (eds): Manières de faire des sons. Paris: L’Harmattan, pp. 45-82.

Vaggione, Horacio (no year): Shifting Mirrors, pour saxophone alto et 32 pistes numériques, note 3 (pdf, two pages) [quoted as Document 1]

Vaggione, Horacio (no year): Shifting Mirrors (2016) pour saxophone alto et électronique, Indications partition normale (one page) [quoted as Document 3]

Schematic Overview