The “singing formant” is a high spectrum envelope peak near 2.8 kHz characteristic of vowel sounds produced in male Western opera and concert singing. An acoustical model of the vocal tract is capable of generating such a peak provided that three conditions are met: (1) The cross-sectional area in the pharynx must be at least six times wider than that of the larynx tube opening. If so, the larynx tube is acoustically mismatched with the rest of the vocal tract, and an extra formant is added to the vocal tract transfer function. (2) The sinus Morgagni must be wide in relation to the rest of the larynx tube. This may tune the frequency of the extra formant to a value between the frequencies of the third and fourth formants in normal speech. (3) The sinus piriformes must be wide. This reduces the frequency of the fifth formant to about 3 kHz. X-ray studies of a raised and lowered larynx showed that these three conditions may be fulfilled when the larynx is lowered. Thus, the larynx lowering, typical of male professional singing, seems to explain the “singing formant” and other formant frequency differences between normal speech and male professional singing.