Perhaps I missed that then because I found no mention of intervals and chords. They seem to explicitly say that they captured pure tones (220Hz for A). This sentence also made it sound as if they were generating a pure note (frequency), "As each note’s unique vibration induced its characteristic pattern into the water, Brown captured it with her camera." Then they went through the chromatic scale capturing each note.

I do wish they posted more about how they set this up. It sounds straight forward and if using pure tones should be easily reproduced...