Which scale degrees are typically identified as unstable in a musical context?

In music theory, certain scale degrees are often regarded as more unstable or dissonant, especially in tonal music. The scale degrees most commonly recognized as unstable are the second degree (2), fourth degree (4), sixth degree (6), and seventh degree (7) of the scale.

The second degree creates tension due to its role as a step away from the tonic and can often seek resolution either upward or downward. The fourth degree is historically treated as an unstable tone, particularly in harmonic contexts, where it often resolves to the third degree (3) or fifth degree (5). The sixth degree tends to be less stable as it can lead back to the tonic or to the seventh degree. Finally, the seventh degree is the most dissonant because it leads directly to the tonic (1); it’s inherently unresolved and creates a strong pull to resolve upwards.

In contrast, the first degree (tonic), third degree (mediant), and fifth degree (dominant) are typically considered stable. They form the foundational harmonic structure of tonal music and are the points around which tension and release occur. Thus, identifying the correct unstable scale degrees is essential for understanding harmonic progressions and resolutions in music.