It all began with a guy named George Vancouver. They named a city after him. George sent a gift of cattle to the king of Hawaii. And that was Kamehameha the First. George told the king to put a taboo on the herd, let it grow. That was ok with the islanders. They didn't know what cattle were. They thought they were like big dogs or something.
Well, this went on until Kamehameha the Third took over, and by that time the islanders had about all the cattle they could stand. They were grumbling about cows tearing up their gardens and endangering the children. So the king called his court together and asked them for ideas. Nobody in Hawaii knew how to handle cattle, but one guy had seen some people in San Diego who knew all about it. So the king went to San Diego to look for these people.
Now doncha know, if you go looking for people to round up cattle you are going to get taken to a rodeo. If you have never seen a rodeo, well, it's very impressive. The king was so impressed he hired everybody. He took about a hundred and fifty guys back to Hawaii with him.
Well, consider the times: if you go to San Diego, in 1830, hiring cowboys, you're going to get a bunch of Mexicans. And some of them are going to play guitars. So after work these guys would sit around their campfires, pull out these guitars, and start playing. This just blew the islanders away. You see, the Hawaiians had never heard music. Hawaiian music was based solely on a singer. They had flutes and drums, but they were never ever played solo, only as backup for a singer. So when one cowboy played a melody and another played the backup, or maybe one fellow played both parts, that was something the islanders had never heard of. Some of them wanted to learn this new instrument, and woodworkers started trying to copy it.
When the cowboys finally went back to San Diego, there was just a slight problem: they had only taught the islanders Spanish tuning, and the islanders kept thinking the strings sounded tense. They kept wanting to relax the strings to get something more appropriate to their ears. So that is what they did. That is why the style is called "slack key". They developed over five dozen different tunings, every one of them tuned below the standard Spanish tuning. The Hawaiians liked the sound of open strings, and many tunes can be played with one hand, no fretting at all. Well, almost.
For a long time the Hawaiians felt like their heritage was being stripped away. They lost their land, their religion, their way of life. They decided they wouldn't let their music go, so the music went underground. For almost 150 years they refused to play for strangers. In the 1970s they began to realize that they didn't have enough people to assure the continuation of their art, so they decided to open up, play their music in public, and accept students from outside their own families. And that is how a music tradition over 150 years old was suddenly dropped on a world that had never heard such sounds.