A Shepard tone, named after Roger Shepard, is a sound consisting of a superposition of sine waves separated by octaves. When played with the base pitch of the tone moving upward or downward, it is referred to as the Shepard scale. This creates the auditory illusion of a tone that continually ascends or descends in pitch, yet which ultimately seems to get no higher or lower. It has been described as a "sonic barber's pole".
Each square in the figure indicates a tone, with any set of squares in vertical alignment together making one Shepard tone. The color of each square indicates the loudness of the note, with purple being the quietest and green the loudest. Overlapping notes that play at the same time are exactly one octave apart, and each scale fades in and fades out so that hearing the beginning or end of any given scale is impossible. As a conceptual example of an ascending Shepard scale, the first tone could be an almost inaudible C(4) (middle C) and a loud C(5) (an octave higher). The next would be a slightly louder C#(4) and a slightly quieter C#(5); the next would be a still louder D(4) and a still quieter D(5). The two frequencies would be equally loud at the middle of the octave (F#), and the eleventh tone would be a loud B(4) and an almost inaudible B(5) with the addition of an almost inaudible B(3). The twelfth tone would then be the same as the first, and the cycle could continue indefinitely. (In other words, each tone consists of two sine waves with frequencies separated by octaves; the intensity of each is a gaussian function of its separation in semitones from a peak frequency, which in the above example would be B(4).)
In a dance hall by the river, I was singing in a traveling band
Just another small town night, with a silver moon shining
I remember when I saw you, that first moment when it all began
You looked across a crowded room and stole my heart away
And we stood out in the moonlight, in the shadow of a factory wall
Music playing soft and low, and a gentle breeze sighing
And the light on the river was magic, yes a magic that I still recall
Moments come and moments go but these moments still remain
Remember how we met, down by the waterside
How easily we forget, all the love that we knew, oh
So we married our fortunes together and we sealed it with a golden band
But somewhere down along the road, we could see the flame dying
Now an exiled heart gets weary, like two strangers in a foreign land
We reached the point of no return, a long, long time ago
Remember how we met, down by the waterside
How easily we forget, all the love that we knew, oh
[Incomprehensible]