What is "Kol ha'Ratzin"?
Radak: It is the voice of Simchah. They were saying "Yechi ha'Melech."
Radak (from Divrei ha'Yamim II, 23:12): They were praising the king.
Radak citing Targum Yonasan: It is the sound of the nation dancing and clapping, like it says "va'Yaku Chaf" (verse 12).
Why does it say "Kol ha'Ratzin ha'Am"?
Radak #1: The word Samuch to ha'Am is omitted. It should say ha'Ratzin Ratzei ha'Am. This is like "Sigim Kesef" (Yechezkel 22:18; it should say Sigim Sigei Kesef), "Amarim Emes"(Mishlei 22:21; it should say Amarim Imrei Emes). In Divrei ha'Yamim II, 23:12 it says "Kol ha'Am ha'Ratzim."
Radak #2, Malbim: The word Kol applies to both. It is as if it says Kol ha'Ratzin v'Es Kol ha'Am.
Why does ha'Ratzin end with Nun, and not with Mem?
Radak: We find like this - "Keta ha'Yamin" (Daniel 12:13) is like ha'Yamim.
