Concept and Technique
The original concept of Virtual DJ was to create a virtual room in which the audience would interact with sound and light by simply moving around with a tracker in hand. With an acknowledgement to the obvious connections with the earlier work of David Rokeby, Virtual DJ is designed as a comparatively populist project, one in which the audience can interact in a very physical, almost aerobic manner to dance-oriented electronic music.

Virtual DJ uses two motion-trackers, one controlling drum and bass, and the second controlling melodies and samples. Borrowing a metaphor from gaming, the piece employs multiple levels of difficulty, with each successive level becoming more complex as the piece progresses. Hot spots in each level allow one user to move the piece to the next level. In addition, certain motions have been standarized to create specific sound effects: raising the hand in the melody tracker usually results in a rising melody, raising the drum and bass tracker results in a change of drum patterns. Similarly lights are used to give the users a physical sense of the sound zones in the room: when users move within sound zones lights dynamically change in synch with their movements.

Performance
As a rule Virtual DJ is first performed by one or two "rehearsed" performers and after this the audience is invited to take the melody tracker while Steve Gibson takes the drum tracker. This allows the interactor to be simultaneously grounded and in a great deal of control. The personalities of these users come to light in very particular ways when interacting with Virtual DJ. This is due to the fact that audience members are aware of the structure of the environment (by viewing the initial rehearsed performance), but at the same time are free to move within the confines of that structure, varying their performance radically from the person who has gone before.

Net Version
A version of Virtual DJ has been developed to allow two geographically-removed performers to interact with the piece simultaneously. With the help of the programmers from APR, a version of the tracking software has been developed to allow positional information to be delivered over a high-speed network, thus allowing the users at each site to hear and see the results of the remote person's motions.

Currently a network performance between Steve Gibson at University of Victoria and Dene Grigar at Texas Woman's University has been tested. In this performance Dene controls the sound and light of the melody tracker in Victoria. Using Apple's iChat software and a camera she sees a projected image of the room in Victoria and hears how she is affecting the audio there. Similarly Steve sees Dene's projected image in his Victoria studio and can infer her movements by a light which moves in a ghostly manner in response to her movements.

Please go to the Virtual DJ video gallery for examples of the network- and other performances.