I grew up with it, so to me it's nothing out of the ordinary. Very distinctive and possibly interesting to you folks from far away.
They also use some interesting techniques, like this thing where you hold a needle and thread in their teeth and bounce it across the strings while playing.
Anyway, cool stuff. Some very famous performers have taken this type of guitar playing
to heart and spent many years pursuing it and those who continue to pass on the old
guitar traditions, even if nobody ever knew about it. Even Stills and the others
spent a lot of time here, writing many of their most famous songs on the very island
where I live.
Interesting stuff imho, though, no doubt you all have your own traditional guitar as well
Common Slack Key Tunings Notes Used
G Major or Taro Patch : D G D G B D
G Wahine : D G D F# B D
D Wahine : D A D F# A C#
Open D : D A D F# A D
C Major or Atta’s C : C G E G C E
Mauna Loa : C G E G A E
C Wahine or Leonard’s C : C G D G B D
C 6 : C G C G A E
Old Mauna Loa : C G C G A D
Open C : C G C E G C
F Wahine : C F C G C E
Open F : C F C F A C
Double Slack F : C F C E A C
Some Examples:
Music:
https://youtu.be/tpfT8AzAl0c
Technique:
https://youtu.be/Vb3NNR0iqu4
Love the colour! How do you think - is it any good for speed metal? Hmmm.... 
