The answer to this question is "Major ninth on the dominant seventh chord V7 usually resolves Appoggiatura or the down by step going to the root of the dominant seventh". This V7 is frequently deleting the ninth functions on the chords as an upward resolving the issue and problem of Appoggiatura which is usually located on the third chord.
Im going to assume you mean in music. It can be used to blend all of the different parts so that they are all equal, or the balance may mean that one part, such as the melody stands out more than any other part. Another way may be to balance out the volume correctly to get optimal reactions.
