The male zebra finch, like many other songbirds, purposely attempts to sing the same song over and over without any variation, including in pitch and volume. This is because singing is primarily a courtship ritual, and females are attracted to high song stereotypy in males. A random song can be selected out of the hundreds sung daily and 80 to 90 percent of the other songs will be pretty much exactly the same.

While the research is of course impressive, it's a bit premature to extrapolate it to humans, or any other animal.