A harp guitar is usually a regular 6 string guitar with any number of additional unstopped strings that can allow for individual plucking. To qualify as a harp guitar, it must have at least one unfretted string lying off the main fretboard. These strings are played open like a harp, not fretted. There are almost limitless configurations. Usually 4 to 6 sub bass strings, sometimes also up to maybe 8 additional high strings.
Tunings for this
guitar vary but if the
standard part of the guitar is tuned to pitch EADGBe then the sub bass
harp strings are usually tuned FGABCD obviously in lower octaves.
I
can't find any suggested tunings for higher strings not pictured here.
Since there are so many configurations for harp guitars,
players
tune strings in keys to fit the songs being played.
I usually refrain from putting external links into tips because they go away sometimes and I have no way of having knowledge to fix the problem but I will embed this video of a Harp Guitar for better understanding of the guitar. Somebody let me know if this link goes away : )