Rashi (from Eichah Rabah 1:38): This is (Radak - the name of the place where they used to pass their children to) Molech. It is called Tofes, for the priests bang on Tupim (drums), so the father will not hear his son's screams when he is scalded by the image of idolatry. Radak - if he would hear, his heart would roar and he would take his son back from them.

Radak #1: The place was a Gei (valley) of a man named Hinom. It belonged to one or all of his sons ¹ . Yoshiyah cast there Neveilos and all Tum'ah, so people would not consider passing their children through fire to Molech ² . This was outside Yerushalayim; all other idolatry houses were in Yerushalayim.

Radak #2: The child would Menahem (scream).

Radak #3: The priests would tell the father 'Hinei Lecha, it is pleasant for you, it will be fragrant for you.'

Radak (based on Eichah Rabah 1:36): There was a hollow idol inside of seven rooms. If one offers flour, they open one of them. If one offers Turim or Bnei Yonah, they open two; a lamb, they open three; a ram, they open four; a calf, they open five; an ox, six. If one offers his son, they open seven. Its face was of a calf; its hands were open, like a man opens to receive from his friend. They ignited it with fire, and the priests put the child into Molech's hands, and he died.