Until then, we mourn - for the way things are, for the way things might have been. And each of us mourns in his or her own way - even with music. No, music is not the Tish b"Av tradition. But if one needs music to mourn, J.J. Goldberg of The Jewish Daily Forward has a playlist. Goldberg says:
The first number couldn’t be anything but “Al Naharot Bavel,” By the Waters of Babylon. The words are from Psalm 137 and tell of the exiles weeping after the destruction of the First Temple on the ninth of Av, 586 BCE: “By the rivers of Babylon, there we sat down, yea we wept when we remembered Zion.” This is the classic version many of us remember, performed by Basya Schechter.