ratios) could only be tuned by combinations of the preceding. Until the advent of polyphony and even later, this remained the basis of the concept of consonance versus dissonance (symphonia versus diaphonia) in Western music theory. In the early Middle Ages, the Latin term translated either armonia or symphonia. Boethius (6th century) characterizes consonance by its sweetness, dissonance by its harshness: "Consonance () is the blending () of a high sound with a low one, sweetly and uniformly () arriving to the ears. Dissonance is the harsh and unhappy percussion () of two sounds mixed together ()". It remains unclear, however, whether this could refer to simultaneous sounds. The case becomes clear, however, with Hucbald of Saint Amand (c. 900), who writes: "Consonance () is the measured and concordant blending () of two sounds, which will come about only when two simultaneous sounds from different sources combine into a single musical whole () ... There are six of these consonances, three simple and three composite, ... octave, fifth, fourth, and octave-plus-fifth, octave-plus-fourth and double octave". According to Johannes de Garlandia: Perfect consonance: unisons and octaves. ( — "[Consonance] is said perfect, when two voices are joined at the same time, so that the one, by audition, cannot be distinguished from the other because of the concordance, and it is called equisonance, as in unison and octave.") Median consonance: fourths and fifths. ( — "Consonances are said median, when two voices are joined at the same time, which neither can be said perfect, nor imperfect, but which partly agree with the perfect, and partly with the imperfect. And they are of two species, namely the fifth and the fourth.") Imperfect consonance: minor and major thirds. (Imperfect consonances are not formally mentioned in the treatise, but the quotation above concerning median consonances does refer to imperfect consonances, and the section on consonances concludes: — "So it appears that there are six species of consonances, that is: unison, octave, fifth, fourth, minor third, major third." The last two appear as imperfect consonances by elimination.) Imperfect dissonance: major sixth (tone + fifth) and minor seventh (minor third + fifth). ( — [Dissonances] are said imperfect, when two voices are joined so that by audition although they can to some extent match, nevertheless they do not concord. And there are two species, namely tone plus fifth and minor third plus fifth.") Median dissonance: tone and