Liveness seems to have different meanings to different musicians and musical researchers [Hagan 14]. From the outset of recording technology until perhaps about 1960, a performance was live to those who personally witnessed it and recorded as it was listened to afterward; recordings were of live performances. More recently, these are heard as “live” (in contrast with recordings of sounds that were never produced on stage but rather were assembled in a studio). Such an artifact is paradoxically called a “live recording” to distinguish it from a “studio recording”.
In laptop performance, even if the music is being generated in real time, the perceived “liveness” of the performance can depend on whether, and how meaningfully, the performer is actually controlling the generation of sound. This could take the form of playing an instrument or adjusting a more abstract collection of controls. Liveness appears less to be a yes-or-no question than to lie along many possible dimensions.
Liveness is used quite differently by acousticians to describe the reflectivity of the surfaces that make up the interior of an enclosed space.
[Hagan 14] Kerry Hagan. “How Live is Real-Time?” Online proceedings, Electroacoustic Music Studies Conference, Berlin, 2014.