That's all very well and good, but there's nothing we've played so far so says we're playing over an A7 chord as opposed to a D7 chord. It'd be nice if we could imply the change that occurs when one chord switches to the other.
One way to imply the change is to emphasize notes that are particular to those chords and to move smoothly between the two. For example, the A7 chord has a C# in it which is the major 3rd (3)
of the chord. The D7 has a C in it which is the flatted 7th (b7)
. There's only a 1 fret difference between the C# of the A7 and the C of the D7:
They lay right next to each other on the fretboard. The example below shows how these two notes sound against their respective chords: