Summoned Voices acts as a living memory of people and place. It consists of a series of door installations each with an intercom, sound system and a computer that is networked to a central file and database server. The design metaphor of the door presents a familiar scenario, that of announcing oneself at a doorway and waiting for a response from persons unknown. Signage instructs the public to speak, make sounds or sing into the intercom. Their voice is stored and interpreted, and results in local playback composed of the individual's voice with those that have gone before. Summoned Voices acts as an interpreter of sound, a message board and an imprint of a community - a place for expression, reflection and surprise.
At first glance the mode of interaction at the door would seem a simple one - pressing a single button and leaving a message. The complexities of the human voice however provide rich material for interpretation by the computer system and participants quickly realise that they can influence the sonic response by varying their voice. For example: a sung voice often recalls other sung material - shouting, more shouting or harsh sounds - whistling, other whistled fragments or even the call tones of mobile phones. Playback lasts between 10 seconds to up to 2 or 3 minutes depending on the length of the message and individuals can interrupt the playback to add new messages for interpretation. Playback occurs after a brief pause when the individual releases the intercom button. Through observation, participants generally leave more than one message. On hearing the response to their first they vary the message, engaging in vocal play exploring the variety of sounds and word combinations they can elicit. Often people engage with the work in small groups taking turns to add messages and commonly improvising around a particular theme or idea. The networked nature of Summoned Voices enables multiple individuals or groups to access the work at once. It also means they share and contribute to the same large pool of information.
Upon interaction the individual's voice is stored by the computer system, which additionally, analyses the speech for salient characteristics. The analysis is sonic rather than semantic and is therefore language independent. Characteristics include such things as: phrase length, pitch and pitch 'shape', loudness, 'roughness', dynamic range etc. Once analysed, the system makes comparisons with previous recordings, finding similar patterns of speech in a database. After speaking, the individual's voice is played back over a loudspeaker system with voice fragments from the past overlaid and juxtaposed. In this fashion, people communicate with past events, past thoughts and past expressions - the qualities of their voice summoning forgotten messages from the installation. The public lends something of themselves through their engagement, and the work is continually replenished and marked with their imprint. Far from passive or fixed, Summoned Voices is an evolving environment where the installation acts as medium, providing dialogue between past and present. .
The work was premiered at the Art In Output Festival at the Technische Universiteit Eindhoven, Netherlands in February-March 2003. Three door installations were assembled on-site using local recycled building materials and the computer system was installed with a small database of sounds prepared in advance in Australia. This database acted as a seed for interaction. Within hours of opening to the public, the new work transformed into something very Dutch, taking on the content, colour and rhythms of the language. It encapsulated the thoughts, expressions, wishes and humour of the various groups that engaged with it. The ambience of the exhibition space also entered the recordings along with sounds related to the installations themselves through people knocking on the doors as they recorded or scraping the stainless-steel speaker grilles. In this way the work chronicled both its social and physical surrounds. Individuals made creative use of the work adding many non-verbal sounds such as mobile phone tones and the sound of portable CD players.
Summoned Voices consists of multiple installations each with a computer and sound system within a chamber at the rear of the door. All computers are connected on a LAN. When the intercom button is pressed the computer records and analyses the sound, saving the audio data as a file and the analysis data to tables in a database on a server computer. The analysis involves segmentation of the audio into bursts at various resolutions - corresponding roughly to sentences, phrases and words or parts of words. These segments are then analysed for a variety of characteristics such as the duration, median pitch, the pitch envelope and spectral characteristics. The computer also determines higher-level characteristics such as whether the recording represents: singing, slow speech, fast speech, whistling and so on. Once this data is saved on the server, the local computer then constructs a search strategy. This is performed on the basis of these high-level findings to find matches for each voice segment within the analysis database of previous recordings. It then loads the appropriate portions of audio files from the server into memory and plays the audio through the sound system using a variety of synthesis algorithms. Summoned Voices was programmed in C on Linux and used the sound language Pd and the database PostgreSQL along with a variety of scripts and utilities.