You speak low, keep your voice up.

[jasonree123456]

You speak loud, keep your voice down.
You speak low, keep your voice up.

What are the antonym for "loud" and "keep your voice down"?

 

[probus]

What are the antonyms for ..

You speak loudly: you speak quietly, or softly, or keep your voice down.

You keep your voice up: this expression does not exist, so it has no antonym.

 

[SoothingDave]

Is someone is speaking too softly (not "low") we ask them to "speak up."

("Low" would refer to pitch of the voice, not volume.)