What is the ruling on quiet songs with ordinary lyrics, given that natural sounds such as birds, water, and wind contain something akin to music, and that Prophet David, peace be upon him, used to seek forgiveness with psalms?

The statement that David (peace be upon him) sought forgiveness through the Psalms has no basis. The meaning of the Prophet's (peace and blessings of Allah be upon him) saying to Abu Musa Al-Ash'ari: "You have been given a mizmar (flute) from the mazamir (flutes) of the family of David" is a simile comparing the beauty of his voice to the sound of a mizmar, because David (peace be upon him) had a very beautiful voice. This is similar to Abu Bakr's statement about singing, that it is the mizmar of Satan, even though the two girls did not have a mizmar with them. However, he called singing the mizmar of Satan, likening it to a mizmar in its ugliness.