Understanding Harmonic Functions

Tonic, dominant, and subdominant chords are fundamental pillars in Western music harmony. They create a structure within a key, guiding listeners through a sense of musical beginning, middle, and end.

The tonic chord is the home base of a key, usually the I chord. It's where music feels at rest. In C major, the tonic chord is a C major triad (C-E-G). It's the starting point and goal of any harmonic progression.

The dominant chord, typically the V chord, creates tension that seeks resolution. It often includes a leading tone that wants to resolve up to the tonic. In C major, the dominant is G major (G-B-D), with B resolving to C.

The subdominant, or IV chord, serves as a bridge between tonic and dominant. It provides a contrasting sound that prepares the ear for the dominant's tension. In C major, it's F major (F-A-C), balancing between rest and motion.

While major keys follow the I-IV-V pattern, minor keys often use i-iv-V or i-iv-v. The chord qualities change, but their functions as tonic, subdominant, and dominant remain the same, providing a framework for tension and resolution.

Secondary dominants are dominant chords that resolve to chords other than the tonic. They momentarily imply a different key, enriching the harmony. For instance, the V/V in C major is D major, which would resolve to the G major chord.

The tritone interval, spanning three whole tones, is crucial in dominant chords. Found between the 3rd and 7th of a dominant seventh chord, it's dissonant and demands resolution, which is why dominant chords are so effective at creating tension.