Spectrogram of the mouthpiece pressure during the performance of pitch adjustments when fingering the tone C#₅ (concert pitch E₅) showing the theoretical fundamental frequency (659.26 Hz; marked as a horizontal dashed line) and the first harmonic. The interval of pitch variation (I_pitch) is considered between the lowest and the highest fundamental frequency achieved during the task. [Mouthpiece no. 6, first repetition].