From Alan Watson, Cardiff, UK
Do bowhead whales produce two sounds simultaneously through the manipulation of overtones as practised by throat-singers, John Velonis asks (Letters, 2 June). I compared sonograms I made of normal singing and throat-singing in humans with one of bowhead whales.
In normal singing, all the harmonics rise and fall in unison. In throat-singing, the sonogram has lines running horizontally across it, representing the constant harmonics of the drone tone. In the whale sonogram there are two unrelated sounds: a series of clicks, which have their own harmonics, and an unrelated rising and falling tone. So it is quite different to throat-singing.
