This video displays the application Callitwhatchawant. Created by by Ivica Ico Bukvic, assistant professor of music, the application is an example of an algorithmic piece whose content and consequently structure are entirely generated by computer in real-time. Bukvic said this piece "marries computer science with music and generates tune based purely on mathematical ratios and forms found in nature."
Harmonic overtones are multiples of a fundamental frequency that maintain perfect mathematical ratios. For instance, a note "A" generates 440 vibrations per second. Therefore, 880 vibrations per second is its harmonic overtone, and so are 1320 and 1760, etc. "When these relationships are translated into traditional music notation," says Bukvic, "the first four overtones produce a major triad, the very foundation of tonal music." See a video of Bukvic.
Link: Excerpt of music from ''Singing Darwin'' (SWF | 1MB)