Harmonics appear as horizontal lines at fixed vertical positions

Evidence

A spectrogram shows which frequency components are present (measured against the vertical axis), at what amplitude (blackness of marking) and when (measured against the horizontal axis). Thus harmonics are represented on spectrograms as horizontal lines, where the vertical position of the line marks the frequency and the horizontal position shows the time for which that harmonic lasts. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1435

Categorization

• DEFINE: Explains how to read a spectrogram: harmonics as horizontal lines whose height marks frequency and length marks duration.