The male tree-hole frog of Borneo has quite a vocal range. But it's not to be compared with that of a great human singer — such as Julie Andrews, for instance. That was the message of Alan Parrish of Ithaca, N.Y., and several other NPR listeners who reacted to a report from NPR's Christopher Joyce on the vigorous vocal efforts of tree-hole frogs seeking mates. Parrish points out that the frog's range covers about two octaves — far less than the five-octave range once enjoyed by Ms. Andrews. NPR's Robert Siegel and NPR's Michele Norris concede the point, and offer an improbable duet — tree-hole frog and musical legend — on "Spoonful of Sugar" from Ms. Andrews' classic film Mary Poppins.