Studies show that the perceived urgency of nonverbal auditory warnings can be systematically manipulated by altering acoustic parameters such as amplitude, frequency, pitch range, speed, inharmonicity
and melodic structure (Edworthy et al.
Inharmonicity is achieved in stages through a downward octave shifting.
The microphony is composed of sustained pitches which, through the twelve repetitions of the process, move in five steps from harmonicity toward inharmonicity as shown on Example 6 (where the inharmonic tones are indicated by black notes).
The harmonic spectra move gradually toward inharmonicity.
As shown in Example 8, the ensemble is divided into four groups labeled A, B, C, and D, with an overall harmonic progression from harmonicity toward inharmonicity.
The change from inharmonicity to harmonicity is also prepared through control of the number of pitches generated in each section.