There are four main voice classifications for choirs: soprano, alto, tenor, and bass. Solo performers have additional sub-classifications within each category, such as coloratura soprano, lyric mezzo-soprano, and dramatic baritone. A singer's voice type depends on their vocal range, where their voice is most comfortable within that range, and the timbre or color of their voice. A voice does not fully mature until the 20s, so a singer's classification may change as they age.