Yester-day, I figured out the single, repeated mellotron note in "The Best Way to Travel" (it's the D an octave above middle C, played with the clarinet sound). I also realized that the single note and the effects applied to it illustrate what the lyrics say: "Thinking is the best way to travel."
As a musical representation of being stationary, there's a single pitch, but because of the effects applied (which I believe is a combination of stereo panning and increasing and decreasing reverb), that one note seems to travel left and right and back and forth. While no actual travelling takes place (the pitch stays the same), those effects (like thinking) give a feeling of movement.
