In responding I remembered a recent trip to the Blue Mountains. There were wonderful sounds of wind in the trees and different species of birds, including black cockatoos.
At night there was less sound and I'd brush my teeth and feel self-conscious of the noise made by my toothbrush.
When I decided to record the toothbrush, I remembered that my kids' toothbrushes all made different pitches. So I collected them together and found I could make chords when recording them going all at once.
The toothbrushes were recorded using a motor from an old blender as an induction coil microphone.