there's a train that goes up along the washington coast and along one section, it crosses a secluded bay on a bridge that's only a few feet above the water and it's barely wide enough for the train tracks. i used to go sit in my canoe in the water next to the bridge and watch the train come by in the evening right after the sun had set. the train would always blow its whistle over and over to make sure no one was on the tracks before it got to the bridge. you could sit there and listen to the whistle bounce off the hills and the water and the islands nearby and it was the most beautiful thing to witness.
for this song, i took my tape recorder out to this exact location and recorded the train blowing its whistle as it approached and passed and i looped the whistle and used it as the main synth in the song. the higher synth that comes in later reminds me of the approaching train whistle as it gets louder and louder and quickly disappears.