An interval is a distance between two notes.
A song is made up of many intervals. An interval has two directions: up or down. Going up has an energizing effect. Coming down is the opposite — calming, settling, depressing, and so on. It basically takes away energy.
The other element of an interval is the distance. Basically, the bigger an interval, the more dramatic/abrupt its effect.
Note that intervals don’t apply just to melodic parts — chords, too, have intervals. Going from root to fifth is a bigger jump in interval than going from root to second. But the effect there is less than what we get from a main melody, for example. Mainly because harmonic intervals typically stay in the background, while melodic intervals concern with the part where listeners pay more attention to. Going a fifth up or down is less common in a melody than in chords.
Example: Big Upward Interval in West Side Story “Maria”
Now that we have the theory down, let’s look at some examples. “Maria” from West Side Story is a good example of an interval that creates a huge impact. Leonard Bernstein’s famous chorus line is a tritone, and the melody goes higher from there, too. The resulting effect is a real attention-catching, energizing moment, followed by a small/steady uplifting.
The most brilliant thing about that famous line at 30 seconds into this video is that the big tritone leap is matched with the “ri” in “ma-RI-a” which is consistent with how we pronounce that name in English, at least to the extent that the strongest syllable is assigned to the big interval. Although tritone is highly dissonant, since it resolves to a harmonious note with a half-step move right away, giving it a smooth finish.
Example: Static Melody in Pet Shop Boys “I Don’t Know What You Want”
On other end of the spectrum, here’s a great example of a melody with as little movement as possible. In “I Don’t Know What You Want (But I Can’t Give It Any More)” from Nightlife, Pet Shop Boys takes lyrics that can come across as very strong, bitter and accusatory and matches it up with mostly one-note lines.
Because of that extremely static melody, PSB effectively tones down the feeling contained in the words and creates a more easily digestible, subtly melancholic atmosphere. When the notes change it goes step-wise downward, resulting in a settling-down feel.
In short, when you think of intervals, think:
- big = dramatic
- small = predictable, smooth
- up = energizing
- down = de-energizing (settling, depressing)
Whether you’re thinking in terms of the main melody or the bass line, knowing the above principle will make you aware of what kind of impact the part is creating and match it up appropriately with other elements.