I read on the internet about a book called : develop a deeper voice by Pierre Kirouac and MAxime Bellemare, it's about getting a deeper voice. Anybody in here read it? If not, anybody in here know how to get a deeper voice? There must be exercices for that somewhere, anybody in here know any?

Sorry man I just have a deep voice. It happened with puberty.
You have the vocal chords you have. Thicker longer vocal chords = deeper voice. Not much you an do about that.

Be happy with what you have and make the most of it. Because that's all you're gonna get.
Try stretching your range like for a warm up. I do this by singing in chromatics and go from my lowest note F to as high as I can go. I found that when I do this, my vocal chords allow me to go two whole steps lower than F. Try that.

You may not deepen your voice dramatically but a few extra notes can't hurt.
We're all alright!
Nice try, Justin Bieber.
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Depends on what you mean by getting a deeper voice. You probably mean a heavier timbre not lower notes right?

The sad truth is that timbre is mostly defined by your vocal type. Range is less relevant to the type. So you may get some lower notes but they wont sound the same way the low notes of a bass do.

One thing you can try though is to sing with a slightly lowered larynx, starting on something like a yawn position.