R1 and R2

R1 For females, R2 for male

Within the vocal mechanism, there are different areas where the voice will resonate, or ‘vibrate.’ The term R1 refers to the resonance area containing the laryngeal space (located inside your neck where your voice box is) and R2 the pharyngeal space (located in the back of the throat). R1 is often called the primary gender control knob, and it will be the most decisive factor in the feminization of the voice. R2 is for male voices.