Tonicization borrows the dominant's pull without changing keys
Any major or minor diatonic chord can be briefly treated as a temporary tonic by preceding it with a chord borrowed from its own key — most often that chord's dominant. This creates a strong local pull toward the target chord while the overall key stays exactly the same. It's the harmonic equivalent of a spotlight briefly shining on one chord.
TonicizationTemporary Tonic
Key Concept 2
A secondary dominant is labeled by "of" logic
V/V means "the dominant of V" — build a major triad or Mm7 chord a perfect fifth above the target chord's root, raising a note to create a new leading tone borrowed from the target's key. The same "x/y" logic (read right to left as "x of y") applies to any secondary chord: the chord after the slash is always the one being tonicized.
V/VSecondary DominantLabeling
Key Concept 3
Secondary leading-tone chords do the same job in a diminished color
Instead of borrowing a major/dominant-quality chord, you can borrow a diminished triad or diminished seventh chord built a half step below the target chord's root (vii°/x, vii°7/x). It tonicizes the same way a secondary dominant would, just with a different, more dissonant sonority — useful for variety and chromatic color.
vii°/xSecondary Leading-Tone
Key Concept 4
Borrowed tendency tones still follow the normal rules
Once you've spelled a secondary chord, part-writing it uses the exact same tendency-tone rules as any dominant or leading-tone chord: the (borrowed) leading tone resolves up by step to the target root, and any chordal seventh resolves down by step. Nothing about "secondary" function changes how tendency tones behave — only where they're borrowed from.
Tendency TonesPart Writing
Tonicization
Temporarily treating a non-tonic chord as if it were its own tonic, typically signaled by a borrowed leading tone.
Secondary Function
Secondary (applied) dominant
A V or V7 chord borrowed from the key of a non-tonic chord and placed right before it to tonicize it.
Secondary Function
V/V ("five of five")
The most common secondary dominant — the dominant chord of the dominant, used to tonicize V.
Secondary Function
V7/x
A secondary dominant seventh chord tonicizing chord x; behaves and resolves exactly like a normal V7.
Secondary Function
Secondary (applied) leading-tone chord
A diminished triad or diminished seventh chord borrowed from a non-tonic chord's key, used to tonicize it instead of a secondary dominant.
Secondary Function
vii°/x, vii°7/x
Labels for a secondary leading-tone triad or fully-diminished seventh chord tonicizing chord x.
Secondary Function
Applied chord
A general term for any secondary dominant or secondary leading-tone chord.
Secondary Function
Borrowed leading tone
The chromatically raised pitch (not in the home key signature) that gives a secondary chord its tonicizing pull; resolves up by step to the target chord's root.
Secondary Function
Chromatic alteration
A pitch outside the key signature — often the clearest sign that secondary function is occurring.
Secondary Function
Modulation (contrast)
A sustained change to a new key; unlike tonicization, the overall key genuinely changes for an extended passage.
Secondary Function
Part writing secondary chords
Applying standard voice-leading rules (leading tone up, chordal seventh down by step) to secondary dominants and leading-tone chords in SATB texture.