Abstract
Sopranos can sing at frequencies that are rather higher than the normal values for the lowest resonance of their vocal tract, but failure to use this resonance would reduce both their vocal power and homogeneity in timbre. We have directly measured the resonance frequencies of the vocal tract of sopranos during singing, and find that, towards the top of their range, they consistently increase the frequency of the lowest resonance to match that of their singing. This significantly increases the loudness and the uniformity of tone, albeit at the expense of comprehensibility.