It is interesting that the author here has to describe what emotional effect Schubert might have intended with his use of keys; when writers today do this, to me it suggests that contemporary readers might not hear this angst themselves. Not only did later Romanticism and Debussy stretch tonality to a point where listeners became more comfortable with hitherto dissonant keys, and so they do not hear things the way Schubert’s listeners would have, but modern pop music is very constrained in its use of modulation so society has lost much of the grammar of Baroque, Classical and Romantic music.