These are the diatonic and chromatic steps between the essential tones.
In a chord, diatonic notes are the passing tones. For example, a C Major triad which is C E G; the passing tones are be D F A and B. In a scale, the chromatic notes are the passing tones.
For example, the C Major scale is C D E F G A B C
The passing tones include Db Eb Gb Ab
These chromatic notes could also be referred to as leading tone. Db is the leading note to D, Eb is the leading note to E
Tones on either side of a primary pitch are called neighour tones…
Upper Neighbor Tones (UNT):
These are diatonic tones
Lower Neighbor Tones (LNT):
These are lower chromatic notes below the triads…
Example: C Major triad: C E G
The upper neighbor tone above C is D while the lower neighbor tone is Db
TRIAD NOTE UNT LNT
C D Db
E F Eb
G A Gb