it's strange isn't it?

Walking to school one day, the following string of thoughts wound their way through my head:

Behind me, I can hear the footsteps of someone I don't know.
The footsteps of high heels. I can tell.
Have you ever listened to high heels marching behind you?
Isn't it strange they have two differnt sounds?
Same person. Same feet. Same shoes. Two sounds.
The stranger behind me bought the shoes at the same store.
These shoes were made in the same far away factory.
What makes a shoe have a higher pitch and another lower?
So I walked, listening to this two tone cadence behind me urging me to walk faster.
Next time you hear them, listen.
It's strange, isn't it? It is.