Q:

What is the meaning of "Tampoco las otras hablan si nosotros no les prestamos la voz" in "Los Santos Inocentes"?

This is from Miguel Delibes, "Los Santos Inocentes". Don't try reading the original because it lacks punctuation, and scripts of who's talking and all sorts of things that make it incomprehensible.
Here is a modified context:

A:

I suppose they are talking about the letter H in Spanish. The first character says that the letter H is silent, but the word the character uses is muda, which can also be used to refer to a person that cannot speak. That's when Facundo asks what does that mean, because every letter in the alphabet is muda (has no voice by itself). That is, letters do not speak, they only represent sounds that WE must utter.
That is what the sentence means: all the other [letters] are also silent, they only have voices when we utter their sounds (lend them their voices).

