You hear it speak, for it has a hard tongue. But it cannot breathe, for it has not a lung. What is it?

“Drum”

A drum does have a 'tongue' in the sense of its drumhead, but it does not utilize it to speak in the same way a bell does, and it can be considered to have air inside, which contradicts the lung part.

“Whistle”

A whistle produces sound by air passing through it, which means it does have a form of 'breathing' contrary to the riddle's statement about lacking lungs.

“Horn”

A horn can produce sound and is often blown into, implying a breathing mechanism, which does not fit with the clue about not having lungs.