Harmony (vertical relationship of notes) and Melody (horizontal relationship
of notes) are closely related.
In fact composers have to consider the effect that the Harmony in a measure
of music has on the Melody in that same measure.
A Melody Note at any given time has one of two relationships to the harmony:
Since “Chord Tones” are part of the harmony there should be no “clash”
between the harmony and the melody note.
Many simple melodies (like nursery rhymes and some pop songs) are made up entirely
of “Chord Tones.”
“Non-Chord Tones” usually add colour and interest to the melody. They
give the melody a more sophisticated relationship with the harmony.
However, “non-chord tones” can also sound “wrong” if they
are not used carefully.
In our “Melodic Analysis” we will mark with an asterisk (*) “Non-Chord”
tones since they have to be treated carefully.
This is a note which is held for a relatively long time so that is adds
“tension” to the harmony.
These notes are marked with a T and are numbered (above the note) as if
added to the harmony. (eg. D on a C chord is T9)
This is a note which is very short or which passes between two chord tones.
It is usually heard melodically and does not add Tension to the harmony.
These notes are marked with an S(scale) (below the note) and are numbered by
their place in the scale created by the Harmony. (eg. D on a C chord would be
S2)
Many non-chord tones are ambiguous and/ or perform both functions, or are sometimes
heard by different people to be performing either function. (Tension or Scale.)
It is more important that non-chord tones be recognized and carefully considered
than to spend a lot of time arguing about how they should be labeled.