What's the difference between an alto and a soprano?

The term alto is one of many vocal range classifications; it refers to the second highest possible vocal range. Just lower than a soprano, an alto range will typically fall from the E or F below middle C to the C or D an octave above it; it's the voice that falls between a tenor and a low, or mezzo, soprano. Alto singers are typically female, but it's entirely possible for a male to fall into the alto category. One a female, it's a voice rich and deep, one that is easily able to convey any sort of emotion. Though the soprano voice is highly coveted in opera and choral singing, the alto voice is very favorable in rock music or other types of popular composition. Karen Carpenter and Toni Braxton represent the allure of such a voice; they are two of the most famous alto singers in popular music.

Alto singers are often known for carrying the weight of the upper register in a choral ensemble. Though the soprano voice is responsible for the majority of a song's melody, the alto voice is what fills out the chord, creating the harmonies absolutely essential to a song's functioning. It's the kind of voice that sometimes goes unnoticed in a choral ensemble (most people hearing a piece for the first time seek out the primary melody), but one that holds the song together; without the alto voice, a piece would feel unfinished, nowhere near as full. As a result, most alto singers have a heightened sense of harmonic vocalizing; it's not uncommon for an alto to naturally sing a lower harmony to any piece of music put in front of them. This is a trait desirable in almost any musical group responsible for writing its own songs; the ability to harmonize and harmonize well is the very basis of an alto singer's craft.