(64) L'espace composé dans l'acousmatique multicanal

4. Composed Space in the Multichannel Acousmatic Idiom (64)

4.1. Definition

(65) L’espace composé dans l’acousmatique multicanal est similaire à son équivalent stéréophonique en ce qu’il est constitué de spectres sonores augmentés et façonnés au fil de leur évolution dans l’espace vertical bidimensionnel. La différence ne tient pas seulement à la répartition et à la superposition des spectres sonores dans l’espace tridimensionnel – dans un champ multicanal plutôt que stéréophonique –, mais dans la conception elle-même de l’espace tridimensionnel dans le champ multicanal.

Composed space in the multichannel acousmatic idiom is similar to composed space in the stereo acousmatic idiom because it also comprises sound spectra that are titrated and shaped as they evolve over time in vertical, bi-dimensional, space.  The difference lies not only in the mapping and superimposition of sound spectra in three-dimensional space – in a multichannel rather than stereo field, – but in the conception, itself, of three-dimensional space in a multichannel field.  (65) A general description of the multichannel acousmatic idiom can provide a foundation for the discussion of the parameters of its composed space.

Although the term ‘multichannel’ implies pluralism by definition (e.g. octophony, surround sound, etc.), the final choice of format is a result of the composer’s imaginative capacity manifested as an aesthetic approach, which governs the management of space in the work, and in turn, influences all compositional decisions.  The aesthetic approach thus guides the choice of multichannel form, which can include, but is not limited to, quadrophony, octophony, or systems such as Ambisonics.[1]  It also aids the composer to determine the position of the channels and corresponding loudspeakers in three-dimensional space, where appropriate to the form, and guides the compositional strategy.  This type of decision-making order helps composers to avoid subjugating their aesthetics to a pre-established multichannel form and loudspeaker array.

(66) Pour la commande de ma pièce acousmatique octophonique Ether en 2001, j’ai tenté de développer une approche acousmatique ancrée dans le mouvement spatial tridimensionnel généré par une double spirale. Bien que le format octophonique était obligatoire, j’ai conçu les positions des haut-parleurs pour arriver à la superposition d’une croix avec un rectangle, tel qu’illustré dans la figure 7 (page suivante), étant donné que c’est cette disposition qui permettraient le rendu le plus convaincant de la double spirale. J’ai ensuite créé le caractère spectral de celle-ci et sa trajectoire spatiale tridimensionnelle, permise par la position des huit haut-parleurs.

The following example, founded upon personal experience and which is the basis for the discussion of space in my octophonic acousmatic work Ether, illustrates how my aesthetic approach influenced such decisions.  Having received a commission for an octophonic, acousmatic work in 2001, I sought to develop an aesthetic approach, which came to be anchored in the three-dimensional spatial movement created by a double spiral.[2]  Although the octophonic format was mandatory, I conceived loudspeaker positions that represented the superimposed shape of a cruciform overlaid with a rectangle, as illustrated in Figure 7 (see next page), since I realised that specific loudspeaker configuration would convey the three-dimensional spatial movement of the double spiral most convincingly.  I then created the spectral character of the double spiral and mapped its three-dimensional spatial trajectory as facilitated by the position of the eight loudspeakers. (66)

 

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[1] In acousmatic composition, surround sound is a type of multichannel audio system, comprising different formats, for example, 5.1, 6.1 and 7.1.  The number before the decimal point refers to the number of discrete channels and the number after the decimal point refers to the number of LFE (low frequency effects) channels.  The loudspeakers, each delivering a discrete channel, are placed in front of and behind the listener, in specific locations as dictated by the format.  Ambisonics can be seen as a type of sound system which is a “[…] reconstruction of the original acoustic wave field” according to Stanley Lipshitz (Ambisonic Network, 2010).  In a definition provided by David Malham, ambisonics can be seen as “[…] a method of recording information about a soundfield and reproducing it over some form of loudspeaker array so as to produce the impression of hearing a true three dimensional sound image”  (Ambisonic Network, 2010).

[2] The commission was offered by Musiques & Recherches, Ohain, Belgium.  Ether was premiered at the Eighth International Acousmatic Festival, L’Espace du Son, in Brussels, Belgium on October 3, 2001.