It is called a score or sheet music.
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A composer.
This is generally called a jukebox musical.
There really is no technical name for someone who impersonates musical instruments and machines. They would simply be called an impersonator of musical instruments and machines.
A numbered musical piece might be called a concerto, an opus, or a composition. It could also be called a symphony.
It is known as an Octave (a musical scale of eight notes).