Why is "a kórház mögött a fiatal orvos zenél" wrong?
I wouldn't call that wrong.
You've placed "a fiatal orvos" just before the verb, so that's the element of the sentence that you are emphasizing. In that case, "a kórház mögött" should be placed after the verb.
Is "a fiatal orvos zenél a kórház mögött" wrong?
But it changes the emphasis. This is sentence "a fiatal orvos zenél kórház mögött", is answer for "Ki" (who is painting behind the hospital) and
"a fiatal orvos kórház mögött zenél" is answer for
"Hol" ? (where is the boy painting?).
I think the first one could answer "What does he do?" as well, that's why I picked that.
Makes music- is that not accusative? So why not zenét but zenél (nominative)
zenél is a verb.
zene = music (nominative)
zenét - music (accusative)
zenél = he/she is making music
Why not 'hátul' instead of 'mögött'?
Never mind, searched for it and I've figured it out.
The term "muzsikál" is a synonym of "zenél", should be accepted in my opinion.
Fair enough, accepted now. Do mind that "muzsikál" is less colloquial, though. :)