A passing tone is a non-chord tone
used to fill in the gap between two other tones. These other tones can belong to the same harmony
, a different harmony, or may perhaps be non-chord tones as well.
Usually the space between the tones the passing tone separates is a some type of 3rd and the passing tone
is given the interval which lies between; this rule is not without exception
and especially during modulation
s one may find a passing tone which seperates two tones of no less than a second apart.