We are spending a week in a friend's house near Hilo, while said friend is away visiting family for the holidays. The house is a little plantation cottage in a village outside Hilo proper, set on a hillside just high enough to see over the neighbors' houses and down to the wide Pacific ocean. (Pictures of the view later, when we get home and I have a cable to transfer them from the camera. As usual, I forgot to bring it.)
The ecosystems of all the Hawaiian islands have been drastically altered over the last two hundred years by the introduction of non-native and often aggressively invasive species, although the effects are different from island to island; Kaua'i, for example, has no mongoose, and hence has a much wider variety of ground-nesting birds than the other islands. Over the years we've been hearing about the coqui frog as one of the most troublesome of the invaders. It's problematic because it eats insects that indigenous species also depend on, but as far as humans are concerned its main characteristic is its incredibly loud song, which sounds "co-QUI, co-QUI" all night long. And I do mean all night long. I was a bit concerned about the noise from the main road just a few blocks away, but cars rushing by at 55 mph are nothing to the sound generated by thousands of quarter-sized frogs.
At a distance the sound melds into something like the chirping of crickets, but much louder; individually, the call "co-QUI" starts low and jumps up a major seventh. Occasionally some individual will make the octave jump, a consonance that strikes the ear immediately as somewhat out of place in the generally jazz-flavored cacophony.