Why Does the Same Chord Sound Different? Which Note Is at the Bottom

A chord is a set of notes, and those notes can be arranged in any vertical order without ceasing to be that chord. Putting the note the chord is named after at the bottom gives the root position, which sounds settled and conclusive. Putting the second note of the chord at the bottom gives the first inversion, which sounds lighter and less final. Putting the third note at the bottom gives the second inversion, which sounds distinctly unstable and demands resolution. The notes are identical in every case and only the lowest one has moved, which demonstrates that the bass note determines a great deal more about how a chord functions than the notes above it.

Several reasons combine to give the lowest note disproportionate weight:

• •It is the most audible line after the melody, since the extremes stand out
• •Its overtones reinforce the notes above it, or conflict with them
• •The ear hears intervals from the bottom upwards
• •A bass line moving stepwise creates continuity that a leaping one does not
• •Certain intervals above the bass are heard as stable and others as requiring resolution
• •Composers therefore treat the bass as a second melody rather than as a support

Choosing a position rather than defaulting to the root is what makes harmony move smoothly. Inverting lets a bass line move by step where root position would force it to leap, which produces the flowing bass lines characteristic of a great deal of music. It varies the weight of a harmony, so a passage can move through several chords without every one sounding like an arrival. It allows the same chord to be used repeatedly without monotony. And particular positions carry specific conventional functions, with the second inversion in particular used immediately before a cadence in an arrangement so standard that it is taught as a formula and is audible at the end of thousands of pieces.

Choosing which note is lowest is one decision and how the remaining notes are distributed is another, called voicing, and it changes the sound as much as the inversion does. Notes packed closely together sound thick and are muddy in a low register, since the intervals between low notes are perceived as beating rather than as harmony, which is why arrangers spread chords out at the bottom and pack them at the top. Doubling a note, meaning sounding it in two octaves, strengthens it and tells the ear which note matters. Leaving a gap in the middle produces an open sound associated with certain styles. And which note is placed on top is heard as the melody whether or not it was intended as one.

Two notations for this exist and both are still in use. Figured bass, developed in the seventeenth century, writes only the bass line with numbers beneath it indicating the intervals above that note, so a performer reads the bass and constructs the harmony from the figures, which is how keyboard players accompanied for two centuries and is still taught for that repertoire. Chord symbols used in popular music and jazz name the chord and add a slash with the bass note where it differs, which states the same information in a way that fits the way those musicians read. Classical analysis uses roman numerals with superscript figures, which combines both ideas.

Rearranging which note of a chord sits lowest changes how settled it sounds without changing which notes are present, with root position stable, first inversion lighter and second inversion demanding resolution. The bass carries disproportionate weight because its overtones reinforce or conflict with what is above. Inverting lets a bass line move by step rather than leap, which is what makes harmony flow.