Hello! Currently I'm studying Albinoni's Adagio and I'm wondering what is it that makes it tick. I can hear a Natural Minor scale as well as Harmonic Minor. I know there are more pieces like this, so I'm wondering how does it happen. In modern music these two not necessarily get along well. These scales are different in 7th step, so it's not even about modes.
How can I learn to use them interchangeably and still make it sound good? My friend says there's a classical harmony on which all the classical pieces are built and there's a modern harmony that's like "It's good as long as it sounds good. Doesn't need to fit the classical rules." But he doesn't want to elaborate.
My only idea is: the certain chords in the background could make the #7 sound well; but how to do it without any backing track? I'm familiar with both scales quite well for a beginner but I can only use them separately. What should I learn to be able to combine them?