I believe A natural is the top line of the bass cleff and D natural the 3rd line of the treble cleff thats not to bad a jump it would be the A string open and the B string on the third fret the note that Steven Stills hits on that high part in Suite Judy Blue Eyes is a whole octive above that (D6) now thats a stretch. I believe this is part of the mathmatics of music theory. It sipmplifies things like the Nasheville System. It is easy to confuse the note D5 for the chord D5 which is a root note in the base a fifth above and an octive above the root leaving out the 3rd. Rockers call that the power chord.