Move the key of G up one string, add a fourth form scale on the G string and you have the mandolin’s second favorite key, D. The key of D has two sharps making both Fs and Cs sharp (played on the fourth fret on the D and A strings.)
Here’s a forms exercise for all four strings in the key of D.
Take Sally in the Garden, in our earlier example we played it on the G, D and A strings. In this version, in the key of D, watch how the fingerings are exactly the same, just moved up to the D, A and E strings.
Niel Gow (the spelling is correct) is Scotland’s great composer of fiddle tunes from the 18th century. It is said that he wrote this tune on the occasion of the death of his second wife, but popular tradition has it that the lamentation actually is for his favorite fiddle which he had dropped and broken. This tune uses all four strings: a 4th form on the G string, a 1st form on the D and A strings, and a second form on the E string.