What is an interval?
In music theory, an interval refers to the distance between two pitches. It essentially measures the difference in height or depth of two notes on a staff. Intervals can be described in two ways:
- Horizontally (melodic): This refers to the distance between two notes played one after another, creating a melody.
- Vertically (harmonic): This describes the distance between two notes played simultaneously, forming a chord.
The different types of intervals
There are two main classifications for intervals based on their quality:
Perfect intervals
These have a pure and consonant sound due to their simple mathematical ratios between their notes. They include:
- Perfect Prime: Two identical notes played together.
- Perfect Fourth: Five whole tones or four semitones apart.
- Perfect Fifth: Seven whole tones or six semitones apart, often considered the cornerstone of Western harmony.
- Perfect Octave: Doubles the pitch of the lower note, with a 2:1 frequency ratio.
Compound intervals
These encompass all other intervals and can be further categorized by quality:
- Major Intervals: These have a wider sound than their perfect or minor counterparts. (e.g., Major Third, Major Sixth)
- Minor Intervals: These have a narrower sound than their perfect or major counterparts. (e.g., Minor Third, Minor Sixth)
- Augmented Intervals: An interval made one half step larger than its perfect or major form. (e.g., Augmented Fourth, Augmented Second)
- Diminished Intervals: An interval made one half step smaller than its perfect or minor form. (e.g., Diminished Fifth, Diminished Third)
Remember, only perfect intervals (unison, fourth, fifth, octave) don't have major or minor variations. For all the other intervals (seconds, thirds, sixths, sevenths), they can be major, minor, augmented, or diminished.
Perfect intervals
In music theory, perfect intervals hold a special place for their pure and consonant sound. There are four types of perfect intervals:
Perfect Prime
This is the most fundamental interval, consisting of two identical notes played together. Imagine striking the same piano key twice – that's a unison. It creates a sense of oneness and stability.
Perfect Fourth
The perfect fourth spans five whole tones or four semitones (half steps). A familiar example is the interval between C and F on a piano. Perfect fourths have a bright, open quality and traditionally functioned as a strong foundation for chords. However, in modern music, they can also be used to create a sense of tension or dissonance.
Perfect Fifth
Often referred to as the cornerstone of Western harmony, the perfect fifth is built on a 3:2 frequency ratio between its notes. Play C and G on a piano to hear this perfect fifth. Perfect fifths are incredibly stable and consonant, making them crucial for building chords and creating a sense of resolution in melodies.
Perfect Octave
The perfect octave doubles the pitch of the lower note. Imagine playing a C on the piano, then the C one octave higher. It has a sense of completion and finality, often used at the end of musical phrases or pieces. The perfect octave also has a simple 2:1 frequency ratio, making it another highly consonant interval.
Pro tip: Always count the naturals first
Why is it important to count the naturals? Because each intervals relates to a natural. So when you look at the interval B-F#, you'll notice that it's a Perfect Fifth. Here you count B-C-D-E-F, and these are 5 naturals.
But intervals can be confusing. An interval can sound like a perfect fifth, but have another name. Let's see how this works by looking at the interval from B to Gb. You'll count 6 naturals (B-C-D-E-F-G). Because of this we know that the interval is a sixt and not a fifth.
