The things you miss when relying on your ears. A buzzard's call, a sound heard a million times an hour, a simple 'mew'. Nothing to it via the crappy human ear but, bang it through a Kay Electric Company 'Vibralyser' (or modern software equivalent) and "Bob's your mother's brother", all the complexity is laid bare. A hum-drum, slightly annoying, 'mew' from Uskmouth, becomes a many-layered squiggly masterpiece. By the way, the lowest 'layer' is the 'fundamental' above which (at exact multiples of the fundamental frequency) sit 'harmonics'; our useless auditory system hears this as a single sound, however, we do experience the harmonics as timbre, the different 'textures' or 'colours' of sound, hard to describe easy to hear (or see in a spectrogram).