So, that 2nd sound with the grouping of sine waves that looks like it's starting to form a saw wave is actually rather close to the natural signal of an electri

So, that 2nd sound with the grouping of sine waves that looks like it's starting to form a saw wave is actually rather close to the natural signal of an electric guitar. When installing pickups into one of my guitars several years ago, I decided I wasn't going to be satisfied by adjusting the height of the pole pieces by ear, nor was I going to be satisfied with with matching the height of the pole pieces to the radius of the fret board, then adjusting by ear. No, I had a hacker space membership and access to a 100Mhz oscilloscope, so I was going match the pole piece height to the fretboard radius, and then use the oscilloscope to tweak pole piece height until the output of each individual string matched amplitude with the others. So there I was, with my guitar running into the oscilloscope, doing my damnedest to pick each string with equal force and watching the amplitude on the scope. And I noticed a curious thing. The initial pluck was a squiggly, kinda-saw-wave-shaped thing, and then as the note decayed, became something more akin the 2nd graph in the OP, and then slowly turned into something rather like a sine wave as the note faded. What happens, is upon picking, there's a lot of higher order harmonics, and other high frequency content, and those higher frequencies quickly decay, and soon you're dealing with mostly just the fundamental and its lower order harmonics.