the structures in your brain do not say "I need to produce a certain amount of pleasure producing molecules because this certain thing is happening." Your brain just does things! It might be, in terms of music, a stimuli tickling a structure(say used for hearing) and really gets that structure swooning releasing all of that stuff.
You could have an identical, less or more powerful reaction in the future, but that is based on other reactions occurring at the same time, which are also based on the structures they are effecting. So, you cannot measure pleasure with a machine because "pleasure" is not the only thing occurring.
Your brain has a lot of stuff going on at the same time that all affects itself.
In my opinion, no. One likes something or they don't, but perhaps the amount of pleasure they receive varies, is what i think your father is trying to convey. One plays music because they like it. If they find playing irritating or frustrating, they simply will not do it. But if they like/get pleasure from it they will return to the stimuli that gave them that pleasure, but a more romantic/natural/divine truth comes into play here, for life never promises you anything.
Life cannot promise you if you play music, as with anything, you will get pleasure, therefore when seeking pleasure one is gambling time in hope for more of pleasure.
Good question! Had a lot to say. Hope it helps.