According to Wikipedia: In quantum mechanics, wave function collapse is said to occur when a wave function—initially in a superposition of several eigenstates—appears to reduce to a single eigenstate due to interaction with the external world; this is called an 'observation'. There are many different interpretations of wave function collapse and there is no agreement, which one is correct?
In nature, the sound waves which are phonons, produced by various instruments comprise of multiple harmonics, which closely resemble a harmonic series. In terms of a frequency, the harmonic series is an arithmetic series. The difference between consecutive harmonics is constant and equal to the fundamental frequency.
When the auditory system is processing this sound wave it's analysing its harmonics and its periodicity. The end result of this complicated analysis is the determination of the "pitch" which is equal to the fundamental, defined as the lowest frequency of the periodic waveform. From pitch, the brain is able to estimate the length of the object producing this sound, important factor from the evolutionary perspective. Pitch being a single value frequency still represents a superposition of the harmonics. Could we in the language of Quantum Mechanics interpret search for the Pitch as a process similar to the collapse of the wave function?