The firs are stiff, the oaks are more flexible. Each tree sways to their own rhythm designed by each one's particular structure, spread, weight and balance. Branches clack and squeek and whistle in a symphony of tones. Listen long enough and you can catch melody, harmony, themes and variations. A low roar, hum, growl rumbles through the woods. The forest gnashing its teeth--the hills here a giant piles of glacial rubble, rounded knobs of basalt. All those swinging trees are being rung down into their roots like tuning forks, grinding in that glacial bone pile. You can feel it through your feet.
John Muir had a great time riding in a swaying Douglas Fir during such a windstorm. You can read his story here: