Finish this quote: " affects music, and music affects " instruments culture heritage universal theme

It would definitely be Culture.

Statement is obvious, Culture affects music, and music affects culture.

In cultures, music is originated by the people living in those cultures and those cultures have a lot of influence on their music. In the same way, some people create innovative music, not bounded by the cultures, and that music affect the cultures.

In this way both affect other other.

your word would be isle.

isle is an island or peninsula especially a small one.

if you add the letter "a" you get aisle, which is a passage between 2 rows of something like chairs, shelves, or something else.