Researchers studying right whale* vocalizations found that they could tell apart individuals based on their voices. Specifically, individual whales differ on the rate of pitch increase, duration, and formants (loud frequencies within harmonics) within "upcalls," one of the most common vocalizations observed.
Meerkats and bats (among many other species) are known to have and to recognize individual voices of their compatriots. But the neat thing about whales is that they can presumably identify friends from miles away, because their vocalization travel for vast distances underwater.
Since two-way communication with cetaceans is becoming a reality, perhaps one day soon we will; gain an even more sophisticated understanding of whale song.
Until then, let this tide you over (pun intended): https://www.youtube.com/watch?v=zSgiXGELjbc
* ETYMOLOGICAL FOOTNOTE! Popular wisdom holds that right whales got their names because they were the "right" whales to hunt, as they often venture near shore, they act docile near boats, and their bodies float when killed.
US researchers say that they can distinguish individual whales based on the sound of the animals' voices. Using a large set of recordings of North Atlantic right whales, they found that detailed analysis of one particular type of call allowed them to single out individual whales. The biologists want to explore whether acoustic identification could be useful for monitoring whales in the wild.