Voices fall into two main natural categories: male (low) voices and female (high) voices. The latter group includes not only women's voices but also the voices of children of either sex and the voices of castrati. Both groups are further subdivided into two kinds generally regarded in theory as having equal ranges but distinct simply in tessitura. According to established principles in all Italian and German conservatoires the lower male voice, the bass, goes from low F up to d′ or e♭′, while the higher male voice, the tenor, pitched a fifth higher than the bass, goes from c up to a′ or b♭′. The bass uses the bass clef, the tenor the tenor clef. Then women's and children's voices correspond exactly to the two male voices an octave higher, dividing into contralto and soprano, the former corresponding to bass, the latter to tenor. So the contralto can go from ƒ up to e♭″ (almost two octaves) like the bass, and the soprano can go from c′ up to high b♭″ like the tenor. The soprano is written on the soprano clef (first line c′), the contralto on the alto clef.

This well-spaced arrangement of the four most distinctive human voices has doubtless much to commend it. But unfortunately it must be recognised as inadequate and risky in certain respects, since it eliminates a great number of precious voices if it is strictly applied in writing for chorus.