The spectrogram for the second Bach passage is shown below. This spectrogram reveals the intricate tonal effects of the passage - the dialectics between the lower pitched notes responded to by the higher pitch, more clipped, chimed notes.
The following portion of the score for BWV 147 (Cantata 147 Herr und Mund und Tat und Leben) shows in the treble clef (at the top of the green rectangle at the left) a near succession of octavely separated scales, showing that Bach nearly produced the Shepard illusion. [See the example from Tchaikovsky's Symphony 6 for a more definitive realization of the illusion.]
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