The term “changing note” is used to describe a variety of non-chord note patterns. What they have in common is that the non-chord note is unaccented, and the figure employs the movement of a step and a leap (in either order). Usually (but not always) the step and the leap are in opposite directions.
Here are examples of changing notes within a single chord. Changing notes can be used singly or in pairs, and can also be used in combination with other types of decoration.
Special mention should be given to the following pattern of two changing notes, which is called the “cambiata”. The step and leap move in the same direction, with the final note moving in the opposite direction. Historically, this is one of the oldest known types of changing note pattern.
Changing notes can occur during a single chord (as in the above examples), or between chords. Here are some changing notes between different chords. This figure is also sometimes called an “échappée”.
Changing notes normally only appear in the soprano or melody line, but may appear in another part in combination with decoration in the melody.
(NB, an accented non-chord which moves by a leap and a step is an appoggiatura).
Here are some changing notes in a piano Allegretto by Haydn, along with a few other types of different melodic decoration:
(x=auxiliary note, ap=appoggiatura, c=changing note, apn=accented passing note)
In the Grade 6 ABRSM theory exam you will not need to use the terms échappée or cambiata. The general term “changing note” is sufficient.