Spectrum and spectrogram analysis for a D'Addario D4 string along the corrosion process in synthetic sweat solution: (a) Spectrum with an original D4 string,
(b) spectrum after three days, (c) spectrum after seven days. (d) Spectrogram with an original D4 string, (e) spectrogram after three days, (f) spectrog r a m a ft er s e ve n
days.