Four-part harmony is a traditional system of organizing chords for four voices: soprano, alto, tenor, and bass. It developed as tonal music became standard and allows for the whole range of human voices. Four-part harmony is used in both vocal and instrumental music, with the orchestral strings often treated as a four-part choir. Learning a musical system of the past, like four-part harmony, provides a foundation for understanding how music works and can be applied to any musical style. Spacing refers to the distribution of notes among the four parts, with guidelines for proper doubling and intervals between voices. (Source: Musical U)