I heard the tune whistled of a little song

As I approached the house, I heard the tune whistled of a little song coming from the upper window. I did not know anything yet, but I listened. The tune stirred my memory and some dormant recollections came to the fore. The music was banal but the whistling was wonderfully sweet, with soft and pleasing notes, unusually pure, as happy and as natural as the song of birds. I stood and listened, enchanted, and at the same time strangely moved without having any kind of accompanying thoughts.