Interval

Interval in Music Theory

In music theory, an interval is the difference in pitch between two notes. This concept is crucial for understanding musical structure, melody, harmony, and chord construction. Intervals are not only the distance between notes but also determine the emotional expression and atmosphere of music. Intervals are typically described by their name, number, and duration.

1. Basic definition of interval

An interval is the distance between two notes; it’s the difference in pitch from one note to another. Intervals can be ascending (from a lower note to a higher one) or descending (from a higher note to a lower one). The length of an interval is determined by two factors: the number of notes (the length of the interval) and the pitch difference between the notes (a semitone or a whole tone).

2. Types of intervals

Intervals can be divided into different types based on their size and nature. The following are the main categories of intervals:

2.1 Classification by interval size

The size of an interval is determined by the pitch difference between two notes, and is usually described in terms of semitones (half-tones) or whole-tones (whole-tones). The size of intervals can be divided into the following types:

2.1.1 Perfect Interval

A perfect interval is a perfectly pitched interval between two notes that is completely stable and free of tension. They are the most common and harmonic intervals in music. Common perfect intervals include:

• Perfect Unison : Two notes that are exactly the same, such as two C notes.
• Perfect Fourth : For example, from C to F, or from G to C, there are 5 semitones between these two notes.
• Perfect Fifth : For example, from C to G, or from F to C, there are 7 semitones between these two notes.
• Perfect Octave : For example, from C to C below or above, there are 12 semitones between the two notes.

2.1.2 Major Interval

A major interval is a larger pitch difference between two notes, but it is not as stable as a perfect interval. Common major intervals include:

• Major Second : For example, from C to D, there is a gap of 2 semitones between these two notes.
• Major Third : For example, from C to E, there is a gap of 4 semitones between these two notes.
• Major Sixth : For example, from C to A, there are 9 semitones between these two notes.
• Major Seventh : For example, from C to B, there are 11 semitones between these two notes.

2.1.3 Minor Interval

Minor intervals are usually a semitone shorter than major intervals, which can make them sound tense or unstable. Common minor intervals include:

• Minor Second : For example, from C to C#, there is a gap of 1 semitone between these two notes.
• Minor Third : For example, from C to E♭, there are 3 semitones between these two notes.
• Minor Sixth : For example, from C to A♭, there are 8 semitones between these two notes.
• Minor Seventh : For example, from C to B♭, there are 10 semitones between these two notes.

2.1.4 Augmented Interval

Augmented intervals refer to raising the pitch of a basic interval by a semitone, making the interval wider. Common augmented intervals include:

• Augmented Second : For example, from C to D#, there is a gap of 3 semitones between these two notes.
• Augmented Fourth : For example, from C to F#, there are 6 semitones between these two notes.
• Augmented Fifth : For example, from C to G#, there is a gap of 8 semitones between these two notes.
• Augmented Seventh : For example, from C to B#, there are 13 semitones between these two notes.

2.1.5 Diminished Interval

Diminished intervals are intervals that lower the pitch by a semitone, making the interval narrower. Common diminished intervals include:

• Diminished Second : For example, from C to D♭, there is a difference of 1 semitone between these two notes.
• Diminished Third : For example, from C to E♭♭, there is a gap of 2 semitones between these two notes.
• Diminished Fifth : For example, from C to G♭, there are 6 semitones between these two notes.
• Diminished Seventh : For example, from C to B♭♭, there are 9 semitones between these two notes.

2.2 Classification by degree of sound

The degree of an interval is determined by the number of notes between two notes. For example, the interval from C to E is a third, and the interval from C to G is a fifth. Interval degrees usually start with Unison and are ranked by the number of notes.

Common pitch scales include:

• Unison : Two notes are identical, with no difference in pitch.
• Second : For example, from C to D, this is the interval of 2 degrees.
• Third : For example, from C to E, this is the interval of 3rd.
• Fourth : For example, from C to F, this is the interval of 4th.
• Fifth : For example, from C to G, this is the interval of 5th.
• Sixth : For example, from C to A, this is the interval of 6 degrees.
• Seventh : For example, from C to B, this is the interval of 7th degree.
• Octave : For example, from C to C, this is an octave.

3. Functions and Applications of Intervals

Intervals have many functions in music, mainly used in the following aspects:

• Melody Construction : Melodies are composed of notes of different intervals. The choice of intervals directly affects the melody’s flow, expression, and emotion.
• Harmonic Construction : A harmony is a chord formed by the simultaneous sounding of notes of different intervals. The choice of intervals in the harmony determines the color and tension of the chord.
• Chord progression : The changes in chord progression are based on the changes in intervals. The changes in intervals can create chord transitions, giving the music a sense of flow and development.
• Emotional expression : Different musical intervals can express different emotions. A larger interval (like a major third) can express openness or positive emotions, while a smaller interval (like a minor second) can express tension or instability.

4. Conclusion

Intervals are a core concept in music theory. They are not only the foundation of melody and harmony, but also key to musical expression. Understanding the sizes and types of intervals, as well as their application in music, helps musicians create richer, more harmonious music. Whether in composition, arranging, or performance, intervals are an indispensable tool, helping musicians understand and express the relationships between notes.

Note: This article was originally written and edited by AI. Editor: Wu Lecheng, Managing Editor: Eric Lok