I don't know much about music but I am trying to find out what the following songs have in common. I have labelled this common feature as "nostalgia", "melancholy" and "longing" but I am still not completely satisfied.
The song at the start of this track:
The flute part:
The first 10 seconds:
Most of this:
I have even tried classifying songs into hot and cold and the songs above seem to lack any "hot element" except for a distant one which stops them from being completely sad and adds an element of happiness. They still however seem to be dominated by a nostalgic "longing" element, as if the happy ending is far away in the distance.