What kind of intervals are classified as discord?

Discordant intervals are often characterized by their tendency to create tension or instability in music. Augmented and diminished intervals are classified as discord because they produce an unsettling sound when played, contrasting with consonant intervals which tend to sound stable and harmonious.

Augmented intervals, which are one semitone larger than a perfect or major interval, often create a sense of yearning or unresolved tension. Diminished intervals, being one semitone smaller than a minor or perfect interval, have a similarly dissonant quality, contributing to a feeling of instability. These intervals are frequently used in music to enhance emotional expression and to create a sense of movement or anticipation.

In contrast, perfect intervals (such as perfect fourths and fifths), consonant intervals (like major and minor thirds and sixths), and simple major and minor intervals typically evoke a sense of resolution and harmony, which is why they do not fall into the category of discord.