Spectral analysis

Why does each musical instrument have its own timbre?

Why does the same musical note played on two different instruments result in different auditory sensations?

The electrical signal produced by the microphone is a faithful image of the sound emitted by the loudspeaker. The oscilloscope shows us this signal as it changes over time. The signal is is periodic and its frequency corresponds to the pitch of the note.

A study of the frequencies, with the aid of a spectrum analyzer, enables us to represent the same signal in a different way.  It is thanks to this frequency analysis that we can explain the differences in timbre among musical instruments.