ok, your answers are emotive. Here is my answers:
(1)
Are the children in the audience listening to music?
The children are listening to sounds. When they understand the
MEANING of these sounds, they are listening to music. “Music” is when you understand it is music. See this:
http://www.youtube.com/watch?v=r_3q3_VdVz8 Musicians understand this is music. To a child it might be a cat jumping on the piano, something meaningless.
(2)
The sounds the children are hearing, is it all music, or only partly?
The sounds remain sounds, unless encoded into music: if the sounds are harmonically played it is “music” (“music” is the harmony, unless you play something “not harmonic”, see the link above: in this case you have to explain it).
(3)
Which of the four sound generating things on stage are musicians? Instruments?
(a) The pianist is a musician. Her singing is a way to express the music.
(b) The VST player on laptop is playing music. The young woman triggering the e-drum is playing music, too.
(c) The tape recorder is playing AUDIO SOUNDS of something that WAS music when performed, but that is NO MORE music, in a musical perspective. Because MUSIC is the THEORY and the CODE, must be logical, writable, editable and readable (MIDI or SCORES). When music is expressed in REAL TIME (with instruments or the voice) it’s MUSIC. When music is RECORDED it is a “playback” of something that was MUSIC at that precise moment. The human brain encodes this sound as “music”, because it WAS music. Like an image in a mirror, so to speak. But the key element is TIME. Music, to be considered “music” must be played in real time. If it is not played in real time it is just the sound of music. Otherwise: it remains music on score sheet or in midi file: because music is a CODE, a LANGUAGE.
(4)
Where is the music in this scenario? The “music” in this scenario is the SHARED CODE, of course: harmony, rhythm, time, counterpoint etc.
(5)
Where in this scene does music stop being music? Music stops being music when the players stop playing the music. And the children clap their hands. The tape recorder can even continue to play, but it does not play “music”: it just reproduces SOUNDS that human mind codifies as “music” (but it is not music, in a musical perspective: that is why “audio tracks” are not “music” and that is why a cd is not "music" but a "recording" of music, from italian "ricordo", meaning "memory", "cord" = corda, in english "rope").