Intervals and chord building are the foundation of reading, writing, and analyzing harmony in music. This cheat sheet helps students quickly identify the distance between notes and use those distances to build chords. It is useful for piano, guitar, choir, band, orchestra, and music theory classes.
Learning these patterns makes chord symbols, key signatures, and harmonies easier to understand.
Key Facts
- A half step is the smallest distance between two adjacent notes on a piano keyboard, such as E to F or B to C.
- A whole step equals two half steps, such as C to D or F to G.
- A major scale follows the pattern W-W-H-W-W-W-H, where W means whole step and H means half step.
- A major triad formula is root + major 3rd + perfect 5th, or 0-4-7 half steps.
- A minor triad formula is root + minor 3rd + perfect 5th, or 0-3-7 half steps.
- A diminished triad formula is root + minor 3rd + diminished 5th, or 0-3-6 half steps.
- An augmented triad formula is root + major 3rd + augmented 5th, or 0-4-8 half steps.
- A dominant seventh chord formula is root + major 3rd + perfect 5th + minor 7th, or 0-4-7-10 half steps.
Vocabulary
- Interval
- An interval is the distance in pitch between two notes.
- Root
- The root is the main note a chord is built from and the note that gives the chord its name.
- Triad
- A triad is a three-note chord built from a root, a third, and a fifth.
- Seventh Chord
- A seventh chord is a four-note chord that adds a seventh above the root to a triad.
- Inversion
- An inversion is a chord position where a note other than the root is the lowest sounding note.
- Chord Symbol
- A chord symbol is a shorthand label, such as C, Am, G7, or Fmaj7, that tells musicians what chord to play.
Common Mistakes to Avoid
- Counting the starting note as one half step is wrong because half steps count the movement between notes, not the number of note names touched.
- Confusing major and minor thirds is wrong because a major third has 4 half steps while a minor third has 3 half steps.
- Spelling chords with the wrong letter names is wrong because chords should be built in stacked thirds, such as C-E-G instead of C-D#-G for a C minor sound.
- Using a major seventh when a dominant seventh is required is wrong because Cmaj7 uses B, while C7 uses Bb.
- Ignoring accidentals in the key or chord symbol is wrong because sharps, flats, and naturals can change the chord quality completely.
Practice Questions
- 1 How many half steps are in a perfect fifth, and what interval is C to G?
- 2 Build an A minor triad using the formula 0-3-7 half steps.
- 3 Write the notes in a G7 chord using the formula root + major 3rd + perfect 5th + minor 7th.
- 4 Explain why the notes C-E-G and E-G-C contain the same chord tones but are not in the same position.
Understanding Intervals & Chord Building
Intervals have two jobs. They describe a measured sound distance, and they show how notes are named on the staff. Both jobs matter.
C to E is some kind of third because the letter names count C, D, E. The exact size makes it a major third. C to E flat is still a third, though it is a minor third.
Students often count piano keys correctly but spell the interval incorrectly. For example, C to D sharp sounds like a minor third, but the letter names make it a second.
Its correct written name is an augmented second. This matters when reading music, writing scales, and understanding why a chord uses a particular accidental.
Chord building begins by stacking thirds above a root. The root gives the chord its letter name, but it is not always the lowest note being played. Start with a root, then choose the kind of third and fifth required by the chord quality.
A chord based on D with F sharp and A is D major because D to F sharp is a major third. Changing only F sharp to F creates D minor. Changing the fifth changes the sense of stability.
Diminished chords sound tense because their fifth is narrowed. Augmented chords sound unsettled because their fifth is widened. These sound differences help musicians recognize chord quality by ear instead of relying only on a chart.
Seventh chords add one more third above a triad. They are common in blues, jazz, pop, film music, and classical music. The seventh often creates a strong pull toward another chord.
In a dominant seventh chord, the third and seventh form a tritone. This interval is especially unstable. In the chord G seven, B and F form that tritone.
When G seven moves to C major, B commonly rises to C while F commonly falls to E. This small movement is called voice leading. Good voice leading makes a chord progression sound connected, even when several notes change.
Inversions change which chord member is at the bottom. A root position chord has its root in the bass. A first inversion chord has its third in the bass.
A second inversion chord has its fifth in the bass. The chord quality stays the same because the notes have not changed. Inversions are useful when a player wants a smoother bass line or needs notes to fit an instrument comfortably.
On piano, practice playing one chord in several inversions without moving every hand position far. On guitar, notice that different chord shapes can contain the same chord tones. When reading chord symbols, identify the root and quality first.
Then check for added numbers, altered notes, or a slash bass note. A symbol such as C slash E means a C chord with E as the lowest sounding note. Careful note spelling, steady counting, and listening for tension or release build reliable harmony skills.