I won't comment on Vaughan Williams's music in particular, but I certainly think music that evokes and celebrates a certain nationality can accurately be described as 'nationalistic'. And I don't see that such a description is any more metaphorical than many of the other descriptions we employ with music: 'sad', 'anguished', 'triumphant', 'relaxing' and also 'spiritual'--though I won't say anything more about what might make music spiritual. One way--though perhaps not the only way--for music to be nationalistic would be for it centrally to include certain melodic, rhythmic, harmonic or intrumental elements that are unique to a given nation. If a composer includes such elements because they will be recognized as deriving from that region, and she moreover uses them in an approving or celebratory fashion, then I think her music is nationalistic. And I don't see that describing it this way is any more metaphorical than rooting for that nation's soccer team, or pridefully ordering its beer.

I'm not sure the Moonlight Sonata is perceived as sad by every person in every culture. This is an empirical question: our perception of music's expressive features has some dependence on the musical culture(s) with which we're familiar, though I gather there's greater cross-cultural uniformity than one might think. The question of how animals or aliens might hear music is also empirical, though I gather there's little evidence that animals respond to music in the ways we do. The philosphical question is why we perceive music as having expressive featues like sadness in the first place. This is puzzling because there's no comfortable place to situate the sadness: listeners don't always or even typically feel sad when perceiving sad music, and music isn't a phenomenon that seems capable of emotions. I wish I had a good account to offer you. One possibility is that we hear music as having an expressive feature when it resembles in some way the vocal quality, body-language or other behavior in which...

You're right that a work of music can't literally feel sad. It's also true that we, the listeners, often (perhaps even typically) don't feel sad when we hear a sad piece of music. In fact, we might feel exhiliration or awe in the presence of a wonderful performance of a sad piece--a slow one in a minor key, for example. (If sad music typically made us sad we probably wouldn't choose to listen to as much of it as we do.) There's no reason to think that the composer or performer(s) of a sad piece of music need to feel sad. So who or what is the subject of the emotions we seem to perceive in music? And come to think of it, unlike garden variety emotions, the emotions that we perceive in music don't have clear objects either. What is the sadness of the music about? Even though the emotions we seem to hear in music have no clear subjects or objects, it often (though not always) seems right to describe music in emotional terms. Saying how this can be is one of the central problems--if not the ...