One of the saddest songs I know, Naked as we came by Iron and Wine, is in a major key. I know the song is sad, and I feel the sorrow deeply and cry, and yet it makes me smile. Beck's Lost Cause, which is also in a major tonality, makes me cry and smile for other reasons; things deeply connected with my whole being, with all my thoughts. If you think that this is easily explainable, it might be.
But the explanation does not matter, at least not for me, in my appreciation of the songs; I react the way I do because of something I see, hear, in the song itself, and that I could try to hint at. In the case of Naked as we came, I'd say something too wordy, perhaps about the sad fate of every loving human, the strength of meeting death bravely, and I could go on indefinitely. But whoever listens to the song can meet me halfway. And, whatever made this discernment possible, bless it - be it nature, culture, or God.