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  • Writer's pictureMary Barton

Journey in the Ear - Key Relationships!

Last time we looked at how a musical sound wave contains all the notes of a major triad corresponding to the note played. For example, playing a “C” on the piano, produces a sound wave with the notes of the C major triad embedded. This is partly why these notes sound wonderful together.

But there are other important tonal relationships inherently occurring within that sound wave that further guide us down the road of harmony and even song structure.

One of those key relationships is the tonic and the dominant.

Next time, we’ll unpack more in-depth:

  • scales

  • tones versus semitones

  • and key signatures

but for now, let’s briefly unpack:

The Tonic

The tonic note of any major or minor scale

is the 1st note of the scale from which the scale derives its name.

For example, the C major scale, starts on C; therefore the tonic note is C. It's called the tonic because it sets the tone for everything else that follows.

If you're playing in C Major and you hit a note that doesn't belong, such as a D sharp, it will jump out at you as not belonging, even if you didn't know you were playing in C major. If you're composing a song, you are composing within a particular key, even if you haven’t consciously settled on a particular key, and it will sound like nails on a chalkboard when you hit a note outside that key. You might be fooling around on the piano and realize hey, I guess, I'm playing in the key of D! You may not have set out to play in the key of D, but when you hit notes that didn't belong, you realized that's the key you were playing in. No one told you they didn't belong – your ear, reacting to and processing the sound waves coming in, told you.

The Dominant

The dominant note of any major or minor scale

is the 5th note of the scale

Each of the 7 consecutive notes of a major or minor scale have 3 different names:

  • A letter name (A, B, C, D, E, F, G, sometimes with sharps or flats)

  • A number name, called a degree (1, 2, 3, 4, 5, 6, 7)

  • A functional or positional name (tonic, dominant etc)

So, in a C major scale, the dominant is G:


1 5

Tonic Dominant

It’s called the dominant because it has a dominant influence in setting musical direction within the key. It prepares the ear to return to the tonic.

That doesn't mean that every time you play a G you must return to C, but rather that the dominant note can exert an effective pull immediately back to the tonic. And it will exert this influence throughout a piece of music. Our ears experience this pull. Why?

Let’s review the first few overtones of a C sound wave for some clues:


1st 2nd 3rd

Fundamental overtone overtone overtone

Note how C and G are always in direct relationship with each other. Ours ear are hearing that strong relationship.

And it’s a double whammy!

Not only when you strike a C on the piano, do you hear a G at the one of the strongest overtones, the 2nd, but also, when you then strike a G, the other naturally occurring intervals of G within the G sound wave itself lineup precisely with the G frequencies occurring within the C sound wave! Our ears pick up this tonal emphasis, and the relational bond that has been created provokes an inescapable influence over any resulting musical context.

Think of it this way - C and G want to be together! The tonic and the dominant want to relate to each other in this way. They want to lead back and forth to each other. They want to function in the way that they function within the wave.

This is why a piece of music will often start on the dominant and move to the tonic, and end in the same fashion, with the dominant note preparing the ear to experience a completed journey on the tonic.

It’s literally been pre-packaged this way! I find that truly amazing!

Check back next time as we unpack more amazing aspects of this journey in the ear called music!


Mark Petersen, Mathematical Harmonies

Leonard Bernstein, The Unanswered Question - Six Talks at Harvard, 1973, Lecture 1: Musical Phonology

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