A more conservative definition would be: Music is harmonious sound created by the playing of instruments as a whole or individually. It is a direct expression of human emotions designed to manipulate and transform the emotion of the listener/listeners. Music is designed to be felt unlike sound which is heard.

Greek philosophers and medieval theorists defined music as tones ordered horizontally as melodies, and vertically as harmonies. Music theory, within this realm, is studied with the presupposition that music is orderly and often pleasant to hear. However, in the 20th century, composers challenged the notion that music had to be pleasant by creating music that explored harsher, darker timbres. The existence of some modern-day genres such as death metal and grindcore, which enjoy an extensive underground following, indicate that even the harshest sounds can be considered music if the listener is so inclined.

20th century composer John Cage disagreed with the notion that music must consist of pleasant, discernible melodies. Instead, he argued that any sounds we can hear can be music, saying, for example, "There is no noise, only sound,"[2]. According to musicologist Jean-Jacques Nattiez (1990 p.47-8,55): "The border between music and noise is always culturally defined--which implies that, even within a single society, this border does not always pass through the same place; in short, there is rarely a consensus.... By all accounts there is no single and intercultural universal concept defining what music might be."

The composer Anton Webern stated "With me, things never turn out as I wish, but only as is ordained for means—I must", which sets out his view of the underlying generative process of music. The German philosopher Johann Wolfgang Von Goethe believed that patterns and forms were the basis of music; he stated that "architecture is frozen music."