Two very distinctive guitar sounds, the steel guitar and the slack key guitar, were born in Hawaii. They are both an integral part of Hawaiian music and a delight to hear. Rather than attempting to describe the styles, sounds, and history, I’ll just provide you with some useful links and videos that feature these two distinctive guitar sounds with Hawaiian roots.
This site provides a brief history and description of the steel guitar. Here’s an excerpt:
Legend has it that around 1880, Joseph Kekuku, a Hawaiian schoolboy, discovered the sound while walking along a railroad track strumming his guitar. He picked up a bolt lying by the track and slid the metal along the strings of his guitar! Intrigued by the sound, he taught himself to play using the back of a knife blade. The steel sound imitates the characteristic vocal vibrato prevalent in Hawaiian singing. He shared his style with others and the sound became popular in Hawaii about 1880. The name ‘steel guitar’ comes from the fact that it’s played with a steel bar, and usually played lying flat.
To hear the sound of the steel guitar, see this video of of the acoustic steel guitar sound.
Slack Key Guitar
From Wikipedia, here’s the description of the slack key guitar:
[A] fingerstyle genre of guitar music that originated in Hawaiʻi. Its name refers to its characteristic tuning: the English term is a translation of the Hawaiian kī hōʻalu, which means “loosen the [tuning] key”. Most slack-key tunings can be achieved by starting with a classically tuned guitar and detuning or “slacking” one or more of the strings until the six strings form a single chord
To hear the sound of the slack key guitar, see this video of popular Hawaiian musician, Ledward Kaapana.