One of the most fascinating aspects of live performances to me, is that of liveness, perhaps most deeply explored by Auslander. For me, the term is most easily explained in conjunction with immediacy: The time with which an action causes a reaction. In a performance context, this would be a DJ scratching a record and an audience perceiving that record-scratch via attached speakers. Another example would be a drummer striking a drum and the sound being immediately audible. Liveness in a performance context often refer to performances that have low (fast) immediacy and utilize instruments that maximize expressiveness. That last aspect is important, as otherwise one could use the definition to claim that a cd player is the epitomy of liveness.
Sergi Jordà contributes a concrete formula defining the efficiency of a musical instrument thusly:
MusicOutputComplexity × PerformerFreedom
PerformerFreedom = PerfFreedMovement × PerfFreedChoice
In very brief terms, his formula states that a musical instruments performance is maximized when it's output complexity is maximized in conjunction with the performers freedom, and the input complexity is minimized. In other words, an efficient musical instrument is one that allows for a lot of flexibility both in terms of output and performer freedom, yet makes it as easy as possible for the performer to supply this input.
With all that out of the way, we can finally return to Variable Immediacy. It's a method with which each performer can separate themselves from liveness to the point that they are comfortable with. Imagine for a moment that you're a novice guitar player. Strumming a single note is difficult at first, but eventually possible to complete in a timely fashion. As the number of notes that must be hit increase, as well as increase in complexity (chords), the act of playing the guitar becomes far more difficult. Learning to do this expediently and accurately is all part and parcel of learning to play a guitar. But what if you could separate yourself from time? What if you could (seamlessly) move into the future and play a few chords, and return to right now and continue your playing. That is variable immediacy. Separating performers from time, allowing them to build and perform more complex compositions.