Hi lik,
I find it to be fairly melancholy. It expresses the history of Israel's relationship with God. Quite honestly, that relationship was rarely good, as God seemed to see it. It talks about how His people didn't understand what God was doing. This is the same cry that God made to Israel through His prophet Isaiah. The ox knows its master, the donkey its owner’s manger, but Israel does not know, my people do not understand.
So yes, I find the song to have a certain amount of melancholy as it describes Israel's dullness in thinking and understanding of what God was working to accomplish through them. However, as a Gentile, we should feel a certain amount of relief that they didn't possibly. Would salvation have come to the whole world if Jesus hadn't died? If Israel had, as Daniel said they were to do, crowned Jesus as their king, would there have been salvation for the rest of us? But, we must temper that with the knowledge that, even though Israel was defiant against God, it all worked out as it was supposed to according to the prophecies of Jesus' sacrifice for sin.
The Scriptures tell us that it was even a part of God's work to harden Israel's heart, but still, they had no understanding of what they were doing. They were merely actors in a great and wonderful and glorious plan of God to save some from His eternal wrath.
God bless you,
In Christ, ted