Shepard’s Scale 

Like the endless staircase, these twelve musical notes go up or down forever. It’s impossible!

Pass your mouse over the dots one at a time in both directions. Listen carefully. Do the notes get higher in one direction and lower in the other? Which note is highest? Lowest?

Each note is really a chord made up of six notes in six different octaves. Volume shifts and ambiguous octave positions make this audio illusion happen.