The Allure of Intervals in Music
Picture a simple melody on a piano, where a few notes blend into something unexpectedly rich and full. That’s the magic of music theory, where basic building blocks like intervals come together to create harmonies that can stir the soul or drive a crowd wild. If you’ve ever wondered about the phrase “50s and 30s make 70s”—a quirky shorthand for how fifths and thirds combine to form seventh chords—you’re not alone. This concept isn’t just abstract jargon; it’s the backbone of countless songs, from jazz improvisations to rock anthems. As someone who’s spent years unraveling these patterns, I find it endlessly rewarding to break it down practically, showing how understanding this can elevate your own playing or composition.
Let’s dive into why fifths and thirds lead to sevenths, exploring the nuts and bolts with real steps you can try, vivid examples from unexpected places, and tips to make it stick. Whether you’re a beginner strumming a guitar or a seasoned producer tweaking tracks, this interplay reveals the emotional depth in music’s architecture.
Grasping the Basics: What Are These Intervals?
Intervals are the distances between notes, like the steps on a staircase that define a building’s height. A third, for instance, skips one note to land on the next, creating that bright, uplifting sound in major chords. A fifth jumps further, spanning three notes, and gives chords their stable, grounded feel—think of it as the foundation of a house that everything else leans on.
Now, when we talk about fifths and thirds “making” sevenths, we’re referring to how stacking these intervals builds more complex chords. A seventh adds an extra layer, extending the chord upward and introducing tension that resolves beautifully. It’s like adding a twist to a story, making it more compelling. In practice, a dominant seventh chord combines a root note, a major third, a perfect fifth, and a minor seventh, which is why that “50s and 30s” lingo pops up—fifth (5) and third (3) intervals pave the way for the seventh (7).
To get hands-on, start by picking up an instrument. If you’re on a keyboard, play a C note, then add an E (that’s your major third) and a G (the perfect fifth). You’ve just made a C major chord. Now, flatten that G by a half-step to F# for the minor seventh, and listen to how it pulls you back to resolution. This isn’t just theory; it’s a gateway to expressing more nuanced emotions in your music.
Actionable Steps to Build Your First Seventh Chord
Ready to experiment? Follow these steps to construct a seventh chord from scratch:
- Choose a root note, like C on a piano or guitar. This is your starting point, the anchor that holds everything together.
- Add the major third: Count up four half-steps from C to E. Strum or play it—notice the cheerful vibe it brings.
- Incorporate the perfect fifth: Go up seven half-steps from C to G. This adds solidity, like bolting down a structure.
- Finally, tack on the minor seventh: From C, count up ten half-steps to B flat. Play the full chord and feel that subtle pull, as if the notes are whispering for resolution.
Once you’re comfortable, vary the rhythm—try holding the chord longer or arpeggiating it. I remember my first time; it felt like discovering a hidden path in a familiar forest, opening up new landscapes in a song I’d played a hundred times.
Real-World Examples: Where Fifths, Thirds, and Sevenths Shine
Music theory isn’t confined to classrooms; it’s alive in the tracks that soundtrack our lives. Take The Beatles’ “A Hard Day’s Night,” where the opening chord—a G7sus4—relies on that fifth-third-seventh magic to create an explosive, anthemic start. Here, the G (fifth from C), B (third from G), and F (seventh from G) blend to evoke a rush of energy, mirroring the song’s theme of exhaustion turning to exhilaration.
Another gem is in Miles Davis’s jazz classic “So What.” The track uses dominant seventh chords built from fifths and thirds to craft a cool, modal vibe. Davis layers these intervals to wander through scales, showing how they can evoke a sense of wandering through a misty city at dawn—familiar yet full of surprises. If you’re composing, try adapting this: Start with a basic progression like C7 to F, and experiment with adding sevenths to mimic that jazz fluidity. The result might surprise you, turning a straightforward tune into something deeply personal and evocative.
A Unique Twist: Applying This in Non-Traditional Genres
Don’t limit yourself to rock or jazz; even electronic music thrives on this. In Daft Punk’s “Around the World,” subtle seventh chords underpin the funky bassline, using fifths and thirds to build layers that loop endlessly, like gears in a well-oiled machine. As a journalist who’s interviewed producers, I’ve heard how tweaking these intervals can transform a beat from mundane to mesmerizing, adding that human touch to digital sounds.
Practical Tips to Master Intervals in Your Playing
Once you’ve grasped the concept, making it second nature is key. Here’s where the fun begins—applying this knowledge to improve your skills without overwhelming yourself. Think of intervals as tools in your kit; the more you use them, the sharper they get.
- Practice daily with a chord progression journal: Jot down new seventh chords you create, noting how they feel emotionally. For example, a C7 might sound triumphant one day and tense the next, depending on context.
- Ear train with everyday sounds: Hum a third, then a fifth, and try to add a seventh from memory. It’s like tuning into a conversation—soon, you’ll hear these intervals in bird calls or traffic noises, sharpening your intuition.
- Experiment with inversions: Flip the chord order, like playing the seventh as the lowest note, to discover fresh textures. In a live set, this could be the difference between a flat performance and one that leaves the audience buzzing.
- Incorporate technology: Use apps like GarageBand or a digital audio workstation to layer intervals visually, then record your creations. I once turned a simple fifth-third combo into a full track this way, and it became a staple in my playlist.
- Collaborate and share: Jam with a friend, challenging each other to build seventh chords on the spot. It’s not just about perfection; it’s about the spark that comes from shared discovery, like two explorers mapping uncharted territory.
Through these tips, you’ll find that what starts as a technical exercise becomes a creative thrill. I’ve seen musicians transform their sound by embracing this, turning “why do 50s and 30s make 70s” into a personal mantra for innovation.
As you keep exploring, remember that music theory is as much about feeling as it is about knowing. Those intervals aren’t just numbers; they’re the threads that weave emotions into sound, waiting for you to pull them together.