The second part of the chorus of this song looks like this:
The first time it goes to the G major chord in measure two, there are two upper neighbor notes (F# and E) descending until it finally gets to the chordal tone.
The second time through the four-bar phrase, there is a melodic sequence sung at a higher pitch. On the A chord this time, G is sung as a blue note (a repeated minor seventh of the chord).
This quality is then echoed when the chord switches to G. Once again, there is an upper neighbor (A), but when it descends to F, it's sung as F natural.