Steve PMHIf you’re reading this, it means that your interest and passion for music is about more than just listening to some pretty instruments and vocals. This deserves praise because not many people try to actually understand music, so, hats off to you!
But as you can probably tell by now, the world of music theory is full of terms that can seem confusing, complicated, or even downright scary to explore.
This is why I’ve made it a mission of mine to make music easier to approach and simpler to get by anyone bold enough to dive deeper into its theories and fundamentals. Today, I’m answering the question: what are intervals in music?
Learning the meaning of an interval is an indispensable step in figuring out how to organize and read music. This is because intervals are one of the foundations of music. Without them, scales and melody chords wouldn’t exist.
In this article, I’ll be explaining what intervals are in music, how they’re categorized, and discussing all the different ways they’re named. Let’s get started!
What are Intervals in Music?
In music, the term interval refers to the pitch difference between any two notes. Or, in other words, the distance in pitch between these two sounds.
Explaining Intervals
As I mentioned above, an interval is a variation in pitch between two sounds. As a result, the larger the interval existing between two notes, the more they’re different in terms of pitch.
The opposite is also true. The smaller the interval we’re talking about between two sounds, the less different they are as far as their pitch goes.
You may have come across an interval described as linear, melodic, or horizontal. All of these refer to tones that possess successive sounds. For example, a melody with two adjacent pitches.
Also, you may have encountered an interval described as harmonic or vertical. These refer to tones possessing simultaneous sounds. For example, the sounds in a chord.
If we want to talk about intervals size-wise, you should know that the variations in pitches they represent are almost always meant for notes of a diatonic scale. The smallest interval in this case is called a semitone.
Smaller than semitones, we have microtones. These are usually created using notes of different types of non-diatonic scales.
The smallest intervals go by the name commas and refer to very tiny discrepancies found in a few tuning systems across enharmonically comparable sounds, for example, C# and Db. Interestingly enough, intervals can be too small for the human ear to pick up.
Interval sizes also have a physical interpretation as the ratio between the frequencies of two sounds. For example, if you consider any two notes that are an octave apart, their frequency ratio will be 2:1.
This means that when a pitch increases successively within the same interval, the frequency will increase exponentially, even though our human ear will only hear register it as a linear increment in pitch. This is why the size of intervals is commonly measured in cents, a logarithmic unit derived from the frequency ratio.
In music theory, the most widely used naming scheme for intervals is based on two of their properties:
- Quality, such as perfect, major, minor, augmented, and diminished.
- Number, such as unison, second, third, and so on.
We’ll discuss all of this in more detail soon enough, but for now, here are a couple of examples: minor 2nd and perfect 4th.
Not only do these names clue us in on the difference in semitones (more about this in a jiffy!) between the lower and upper notes, but they also identify the spelling of the interval.
Laying the Basis for Understanding Intervals
Wow! That was a lot of information to absorb, so how about we go back to the very basis of an interval — its building blocks. I’m referring to semitones (also known as half steps) and tones (also called whole steps).
Musicians use numerous combinations of semitones and tones to form all the various kinds of chords and scales that create different sounds in music. Let’s take a closer look at each one:
Semitones
As far as western music is concerned, the semitone is the smallest interval size possible and it refers to the very next lower or higher note. In the United States, it’s known as a half step.
An example of a semitone is from C to C# (C sharp) on a piano or from E to F.
Tones
Since the term ‘semi’ means half, it makes sense for us to think of a semitone as half of a tone. This means that a tone or a whole step is an interval that consists of two semitones.
Naming Intervals
Now that you’re familiar with the building blocks of intervals; the semitones and tones (the two smallest intervals in western music), we can move on to look at larger intervals and how you can name them.
In music, an interval gets its name by combining two factors: the number and the quality.
Number of Intervals
First, we’ll discuss the number of intervals. Assigning a number to an interval depends on counting the number of staff positions or letter names of the musical alphabet encompassed in the interval between the two notes, including the letters corresponding to the two notes making up the interval.
Here are a few examples to help you understand this concept:
- The distance between the notes C and D includes 2 letter names. This means it’s an interval of a 2nd.
- The distance between the notes C and E includes 3 letter names. This means it’s an interval of a 3rd.
- The distance between the notes C and F includes 4 letter names. This means it’s an interval of a 4th.
- The distance between the notes C and G includes 5 letter names. This means it’s an interval of a 5th.
- Continuing along the same lines, the distance between the notes C and A includes 6 letter notes, so it’s an interval of a 6th.
- The distance between the notes C and B includes 7 letter names. This means it’s an interval of a 7th.
- Finally, The distance between the notes C and the C above it includes 8 letter names. This means it’s an interval of an 8th.
However, no one really uses 8th to describe such an interval. Instead, it’s commonly referred to as an 8ve or octave.
This name is inspired by the octagon shape, which possesses 8 sides. Whenever you come across the interval octave, your mind should immediately think 8 notes higher than the starting note.
A Unison Interval
If you’ve been paying attention, then you’ve probably noticed that I started the number examples with an interval of a 2nd. Does this mean there’s no 1st?
Well, not quite. An interval of a “1st” would mean that it’s the same note. This does happen, for instance, in a piece of music when two instruments play the same exact note.
Such an interval is known as a unison. In a music sheet featuring a harmonic unison interval (more on this topic below), you’ll see the notes written next to each other.
Interval Quality (Types of Intervals)
There are 5 types of interval qualities, we’ll explain each one below:
1. Perfect Intervals
When we say an interval is perfect, we’re usually referring to one of 3 intervals: a perfect 4th, a perfect 5th, or an octave (a perfect 8ve).
For an interval to possess the “perfect” quality, its upper note must be present in the major scale of the lower sound. As such, an interval of a 4th, 5th, or 8ve isn’t a perfect interval if it’s not on the major scale.
For example, The distance between the notes C and F# is an interval of a 4th, but it’s not a perfect 4th because F# (the upper note) isn’t present on the C major scale.
2. Major Intervals
When we say an interval is major, we’re usually referring to one of 4 intervals: a major 2nd, a major 3rd, a major 6th, or a major 7th.
As such, if the upper note of a given interval is present in the major scale of the lower sound and isn’t an interval of a 4th, 5th, or an octave, this means it’s a major interval.
To easily answer questions about the quality of intervals, you should first figure out the interval’s number starting from the lower note as your number 1. Then, proceed to count the letter names until you reach the higher note.
If you find that the upper note is present on the major scale of the lower sound, you can safely deduce that the interval is either a perfect or a major interval. If the interval is a 4th, 5th, or an octave, then your answer is a perfect interval. Otherwise, your answer should be a major interval.
This is true for any major scale. As long as the lower sound is the tonic and its major scale is where the upper note lies, the interval will always either be perfect or major.
3. Minor Intervals
A minor interval is basically any major interval that’s been made smaller by a single semitone or a half step. For example, if you take the interval of C to E -a major 3rd- and flatten it to the E so it becomes an Eb, the interval will be a minor 3rd.
Since the major intervals are only 4, the minor intervals are also only 4. These are a minor 2nd, a minor 3rd, a minor 6ths, and a minor 7th.
To sum up, if the interval in question is lower than a major interval by a semitone, it’s going to be a minor interval.
4. Augmented Intervals
Think of an augmented interval as the opposite of a minor interval. So instead of taking a major interval and making it smaller by a single semitone, we’ll take a major or perfect interval and extend it by a single semitone while keeping the same letter name.
For example, if you take the interval of F to G -a major 2nd- and expand the G so it becomes a G#, the interval will be an augmented 2nd.
This also goes for perfect intervals. For example, if you take the interval of F to C -a perfect 5th- and widen the C so it becomes a C#, the interval is going to be an augmented 5th.
5. Diminished Intervals
By now, I hope you’re curious about what we’ll get if we make a perfect interval smaller by a single semitone or a half step. If you are, then you’re ready to learn about the last interval quality; a diminished interval.
If we consider a perfect interval, whether it’s 4th, 5th, or an octave, and flatten it by a semitone, it won’t become minor (as with major intervals), but it’ll be a diminished interval instead.
For example, if you take the interval of A to D -a perfect 4th- and flatten the D so it becomes a Db, the interval will be a diminished 4th.
Another way we can form a diminished interval is by flattening minor intervals by a single semitone or a half step.
For example, if you take the interval of E to D -a minor 7th- and make the D smaller so it becomes a Db, the interval will be a diminished 7th.
So, to sum this interval quality up, you’ll get a diminished interval if you:
- Flatten a perfect interval by a single semitone.
- Flatten a minor interval by a single semitone.
- Flatten a major interval by two semitones; a tone.
What are Compound Intervals?
Up until now, I only mentioned intervals up to one octave. Why?
Because intervals larger than that are called compound intervals. Such intervals are an article on their own.
What are Harmonic Intervals?
Harmonic intervals describe when two notes are played “in harmony” at the same time.
What are Melodic Intervals?
These are the opposite of harmonic intervals. They describe when two notes are played “as part of a melody” in succession (one after the other).
