1)
How will He cease their song?
1.
Radak: They used to sing amidst Simchah and great good. (This will cease.)
2.
Malbim: This is like it says "Kechi Kinor Sobi Ir Zonah Nishkachah" (Yeshayah 23:16). It depicts that after Melech Ashur destroyed it in the days of Chizkiyah, it was rebuilt. It is as if it took a harp and sang to remind those who were Mezanah with her (merchants) to return to her for business. Now I will cease her songs and harp; they will not be heard in the future.