The song of the humpback whale is probably one of the most distinctive animal songs in the world. The humpback whale has gained its notoriety for its distinctive song. Technically a humpback whale song is not even a song, it is a way for the whales to communicate with each other. But as humans, it is interpreted as a song. The pattern of the pitch and tone of the communication is what gives it the sound of a song as we recognize it. The only other group of whale that produces these regular vocalizations if the Blue Whale.
While both male and female humpback whales are capable of producing the familiar songs only the males do so, the most notable are the males vocalizations during mating season. Most of the other "songs" are short and not nearly as complex. It is thought that the complexity of the male's song is to make him a more attractive candidate for a mate. It is also being studied as to whether the song is a "flirting" type of behavior or a way for the male to let other males in the area know where his territory is. Both behaviors have been observed. Singing has been observed in situations where one male is accompanying one female prior to mating. It has also been observed in competitive groups of multiple males and one female. So perhaps the song serves both purposes.
The songs are broken down into many complex parts. A few seconds of a single tone are called a unit. Several different units make up a sub-phrase, which is usually less than ten seconds in length. One or two differing sub-phrases are considered a phrase. A whale will typically repeat the same phrase over the course of two to four minutes. This combination of phrases is called the theme. A collection of several different themes are what make up the complete song. They can last anywhere from twenty to thirty minutes and can be repeated for hours or in some cases even several days.
It is known that all the whales in the same vicinity will sing nearly the same song with very little variation between them. All whales in different geographical areas have differing songs so that they can differentiate between whales of their own pod and whales of another. The song of the humpback whale also changes year to year. There is no set amount of method to the changes. Some years only one note may change in frequency or length, other years whole themes may change. The reasons for this are still being researched. Ongoing research also suggests that once a song evolves, the old pattern is never revisited. One research agency studied 19 years worth of whales songs and found general patterns over the years, but the exact same pattern never occurred more than once.