The term "consonance" comes from the Latin consonare which means simply `sounding together'. In early western music theory the term became synonymous with a harmonic interval. However, later theorists used the term to refer to particularly euphonious or harmonious intervals. From there, the term was generalized to triads, tetrads and then to sonorities generated by any number of tones.
In both theoretical and experimental writings, researchers have used a wide variety of terms. These have included terms such as: pleasant, unpleasant, euphonious, beautiful, ugly, rough, smooth, fused, pure, diffuse, tense, and relaxed. Some researchers have treated such terms as synonymous. Others have assumed that the differences are minor -- that is, when asked to judge how ______ a sound is, listeners will respond in roughly the same manner. Other research have assumed that each of these terms generates an entirely different response.
Van de Geer, Levelt & Plomp (1962) carried out an important study where they asked Dutch listeners to judge tone pairs according to ten different scales:
Non-musician listeners judged each harmonic interval using a 7-point scale for each semantic term. Using factor analysis, van de Geer, Levelt and Plomp found that the responses grouped into three independent factors. The analysis produced three statistically significant factors. One factor (dubbed pitch) included the scales high, sharp, tense, narrow, and active. A second factor (dubbed pleasantness) included the scales euphonious, consonant, and beautiful. A third factor (dubbed fusion) included the scales rough, more tones and fusion.
English Dutch high-low (hoog-laag) sharp-round (scherp-rond) beautiful-ugly (mooi-lelijk) active-passive (actief-passief) consonance-dissonant (consonant-dissonant) euphonious-diseuphonious (welluidend-onweeluidend) wide-narrow (wijd-nauw) sounds like one tone-sounds like more tones (klinkt als een toon-klinkt als meer tonen) tense-quiet (gespanen-rustig) rough-smooth (ruw-glad)
The first factor (pitch) was found to correlate directly with the mean frequency of the pitches used in the interval.
Van de Geer, Levelt and Plomp (1962) made the following three conclusions in their study:
The main lesson from Van de Geer, Levelt and Plomp (1962) is that care must be taken when instructing listeners to judge intervals. Some terms are largely synonymous (such as euphonious and pleasant), whereas other terms are not interchangeable (such as pleasant and fused).