I want to make some super-nerd comments. When a string is first plucked it briefly supports all possible frequencies. After a short time, it settles down and supports only the harmonics. Coming cold to this, the slow background continuum looks like that.

The strengths of the harmonics (correctly described as the area under the peaks) are not certain to follow any pattern. Think about plucking a harmonic tone by touching the center of the string. This has zero power in the fundamental. The spectrum really depends on how the string is plucked.

The width of the harmonic peaks is ultimately limited by the time that the tone is sustained. In this case that’s probably the averaging time of the instrument. The longer the tone, the narrower the width. In fact, the width of the peak multiplied by the length of the sound equals one. Said differently, the better you know the time of the tone, the less you know the tone frequency. This “uncertainty principle” is built into the math. Think of a really short tone on a synthesizer. It’s almost a click, and has a huge range of frequencies. Only a very long note has a single precise frequency.

In quantum mechanics, particles are waves, and this exact effect means that you can’t know, for example, both the exact position and exact velocity at the same time. The Heisenberg uncertainty principle. It isn’t really from quantum mechanics: it’s from music.