Writing chords for a musical measure takes careful analysis and consideration of several musical factors. When asked to write chords for a measure, the first step is to examine the notated pitches within that bar of music. You’ll need to identify the key signature, any accidentals, and the melodic notes that occur on stronger and weaker beats. From there, you can deduce the chords that are harmonically compatible with those notes.
Some additional contexts to think about include the genre or style of the piece, as certain chord progressions are more common or idiomatic to particular styles like pop, rock, jazz, or classical music. The surrounding measures before and after should also be analyzed to get a sense of the overall harmonic movement and progression of the song or piece. Considering factors like these will help ensure the chords you write fit musically within the given context.
With just the pitches given in a single measure, there may be some ambiguity as to the intended chords. Multiple chord options could work harmonically. In those cases, it becomes helpful to think about what might be most common or idiomatic for the style. You could also consider functionality – whether the chord serves more of a tonic, predominant, or dominant role within the key and larger harmonic context.
Let’s look at a specific example to demonstrate the process. Consider a measure in the key of C major containing the pitches C, E, G, and B. We can deduce a few things right away:
The key signature has no sharps or flats, indicating the key of C major or A minor.
C and G are part of the C major triad, the tonic chord.
E and B do not clash with a C major chord.
Some potential chord options that would harmonize these notes include:
C major: A simple C major triad would work well as the tonic chord.
G major: G is the 5th scale degree, so a G major chord preceding or following a C major could imply a perfect authentic cadence, a very common Classical progression.
C/G: A first inversion C chord with G in the bass allows all four notes to be included harmonically.
Cmaj7: Adding the 7th scale degree B creates an extended C major 7th chord, common in jazz and popular styles.
Without knowing more context, C major or C/G would be safe assumptions that incorporate all the given pitches idiomatically. But other choices are defensible depending on additional factors about the piece.
The process gets more complex when multiple notes are melody are occurring simultaneously, like intervals above a bass line. In those instances, it requires recognizing common chord types that contain those intervals, such as seventh chords, extended chords, polychords, or even non-tertian sonorities.
It’s also useful to consider voice leading when deciding how chords should connect over time. Smooth melodic motion between chord tones helps produce shapely harmonic progressions. Jumps or leaps between chord tones should usually be avoided, as they can create awkward dissonance or sound unnatural to the ear.
Roman numeral analysis can provide conceptual clarity when working out chord progressions. Labeling chords as roman numerals of their scale degree function helps identify their role within the larger harmonic framework – whether they are tonic (I), predominant (ii, iii, IV, V), or dominant (V) chords. Understanding a chord’s function is key to writing progressions that have direction, momentum, and satisfy harmonic goals like cadences.
When writing multiple chords over a span of measures, one must consider larger scale form and harmonic rhythm. Simple binary, ternary, and rounded binary forms follow common harmonic patterns of repetition, contrast, and return. Cadences should be used strategically to delineate sections and provide closure. Harmonic rhythm, the pacing of chord changes, helps determine the overall gesture and feel of a passage – whether it remains static, moves at a walking pace, or charges ahead quickly.
Effectively writing chords to accompany a given melody or set of pitches involves careful musical analysis and an understanding of factors like musical context and style, functional harmony, voice leading principles, chord types, Roman numeral analysis, form and large-scale structure. With practice, these skills continue developing one’s abilities to provide musical accompaniment and write progressions that complement and enrich a melody. Let me know if any part of the process needs further explanation when completing chord analyses or writing progressions in the future.