The above diagram shows the analyzer of waveform taken from a song. I wanted to know in terms of acoustics how is it that the different frequencies are produced at the same time by the same source. I know about interference but don't know how it works. The same is the case with our ears, we hear different frequencies from different sources at the same instant of time, but our ear drums can vibrate only at one frequency at a particular instant.
How does it work?