Here misery is considered in relation to the people's lost possessions. First, as persons' offices as stated: "The old men have quit the city gate." Namely, exercising their office at the city gate.
Then: "the young men their music": That is, as exercising their office as leaders in chorusing. As I Maccabees 2:9 refers: Her babes have been killed in her streets, her youths by the sword of the foe."