Nothing is hidden ¹  that will not be revealed, ²  and nothing is secret that will not be made known.

“Do ¹  not be afraid of them, for nothing is hidden ²  that will not be revealed, ³  and nothing is secret that will not be made known.

It is similar for lifeless things that make a sound, like a flute or harp. Unless they make a distinction in the notes, how can what is played on the flute or harp be understood?

It is the same for you. If you do not speak clearly with your tongue, how will anyone know what is being said? For you will be speaking into the air.