Musical texture is the overall sound of a piece of music or song. The texture of a piece or song is determined by how the melodic, rhythmic, and harmonic materials are combined in a composition, thus determining the overall nature of the sound in a piece. Texture is often described in regard to the density, or thickness, and range, or width, between lowest and highest pitches, in relative terms as well as more specifically distinguished according to the number of voices, or parts, and the relationship between these voices (see common types below). For example, a thick texture contains many 'layers' of instruments. One of these layers could be a string section, or another brass. The thickness also is affected by the amount and the richness of the instruments. Texture is commonly described according to the number of and relationship between parts or lines of music: