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).
It is called a 'score'
It is called a 'score'
It is called a 'score'
A composer.
score
score
score
It is called an autograph.
A blueprint is now called a blackline. There is no difference between them other than the blueprint was printed on blue paper
amanuensis
Manuscript
Mona Mender has written: 'Music manuscript preparation' -- subject(s): Musical notation