I am working on synthesis modelling of guitars, and I have managed to capture most elements of the guitar well so far. Something I am struggling to understand is why a guitar string has a natural "beating" sound to it, meaning it sounds as if it is ebbing and flowing slowly as it vibrates. To illustrate what I mean, here is a sound file of a guitar string plucked once: https://filebin.net/wo4borxaxe74nbg2 If you listen, it sounds as if the pitch is almost slowly fluctuating up and down over time, or the volume is increasing and decreasing. I have done a pitch analysis, and it doesn't appear to be a true pitch fluctuation: The fundamental note and harmonics all appear to have a very steady pitch over time. However, what can be seen particularly with the second harmonic is that this harmonic comes and goes in intensity over the duration of the note. All the higher harmonics can be easily seen to do this. It would appear this is what creates the "ebbing and flowing" sound. I found one post online which seemed to try to explain this behavior: "Unlike the ideal mathematical model, strings vibrate in two dimensions. Since the change in tension is more pronounced in one dimension than the other, we're actually hearing two sounds. This causes some harmonics to get cancelled while others become more pronounced. As the frequencies of these two vibrations shift relative to each other, the harmonics that get cancelled or become pronounced also change. This causes a slight chorusing or flanging effect. It's also an inherent limitation of plucked string instruments but it's also OK, it's also part of the sound we know and love." https://music.stackexchange.com/que...-a-guitar-why-is-it-only-in-tune-for-a-moment I am wondering if this is the correct explanation for why this happens? If so, can anyone elaborate further? I am trying to understand what they mean by the string "vibrating in two dimensions" or how this creates this phasing/chorusing/flanging effect. Thanks.