If you’re a music student or enthusiast, you may have come across the term “interval class” in your studies. But what exactly does it mean?

In music theory, an interval is the distance between two notes. For example, the distance between C and E is a third.

But when we talk about interval class, we’re not just talking about the specific distance between two notes. Instead, we’re looking at the overall relationship between them, regardless of their specific pitch.

So what does that mean? Let’s break it down.

What Is Interval Class?

Interval class is a way to group together intervals that share similar qualities. Specifically, it takes into account two aspects of an interval:

1. The number of semitones (half-steps) between the two notes.

2. The inversion of the interval (i.e., whether it’s played from low to high or high to low).

By considering these two factors, we can categorize intervals into six different classes.

The Six Interval Classes

Class 0: This includes all perfect unisons and octaves (e.g., C to C or C to C an octave higher). These intervals have a distance of 0 semitones and are their own inverse.

Class 1: This includes all minor seconds and major sevenths (e., C to Db or C to B). These intervals have a distance of 1 semitone and are inverses of each other.

Class 2: This includes all major seconds and minor sevenths (e., C to D or C to Bb). These intervals have a distance of 2 semitones and are inverses of each other.

Class 3: This includes all minor thirds and major sixths (e., C to Eb or C to A). These intervals have a distance of 3 semitones and are inverses of each other.

Class 4: This includes all major thirds and minor sixths (e., C to E or C to Ab). These intervals have a distance of 4 semitones and are inverses of each other.

Class 5: This includes all tritones (e., C to F# or C to Gb). These intervals have a distance of 6 semitones and are their own inverse.

Why Interval Class Matters

So why is interval class important? For one, it allows us to compare and analyze different pieces of music more easily. By grouping together intervals based on their overall relationship, we can better understand the harmonic structure of a piece.

Additionally, interval class can be used in composition. By consciously choosing certain interval classes, composers can create specific moods or effects in their music. For example, using mostly class 4 intervals can create a sense of tension or instability, while using mostly class 3 intervals can create a more melancholy or introspective mood.

Conclusion

In summary, interval class is a way to categorize intervals based on their overall relationship, regardless of specific pitch. There are six different classes based on the number of semitones between the two notes and whether the interval is played from low to high or high to low. Understanding interval class can help with analysis and composition in music theory.