The range of a singer's voice depends on several factors, including the length and elasticity of their vocal cords, the shape of their vocal tract, and their breathing skills. The length and elasticity of the vocal cords determine the pitch range that a singer can produce, while the shape of the vocal tract affects the resonance and tone of the voice. Good breathing skills are essential for providing adequate air pressure to the vocal cords and for maintaining vocal health. Additionally, the development of vocal technique and practice can also play a role in extending a singer's vocal range.