Although it is unwise to take a developmental view of an art like music -- as if Beethoven were an advance over Josquin, or Miles Davis an advance over Louis Armstrong -- there are ways in which it makes sense to talk about musical knowledge growing over time  We certainly know more about certain sounds than was known five centuries ago; that is, we understand how sounds that earlier composers avoided can be used effectively in musical compositions
For example, we now know how the interval of the third, which is considered dissonant, can be used in compositions to create consonant musical phrases
Sounds that were once considered dissonant are more pleasing to modern listeners.