I’ll bet you could recollect one of the first songs or nursery rhymes you learned as a child in a few moments’ time. (“Wee Willie Winkie”, anyone?) Or if I asked you to hum the beginning of the “Imperial March” from Star Wars (i.e., the Vader theme) or the “Raider’s March” from Indiana Jones, you could bring it to mind immediately. Younger folk would likely be able to recall the opening bars of Harry Potter’s “Hedwig’s Theme” , "Let it Go" from Frozen, or “The Mandalorian” without too much thought.
If you could pick a “universal” song that would be recognized in most of the world, which would it be? Perhaps we’d pick the same one: I’d choose what is commonly sung multiple times a year and orally passed down from generation to generation. Can you guess it? Right - “Happy Birthday”! How might we classify what a melody is and why are we able to effectively summon them from memory?
Simply put, a melody is a string of notes heard in succession within a rhythmic framework. Melodies are formed from smaller units called phrases, which may be described as musical sentences. Often, melodies consist of a question/answer idea: the initial phrase makes a statement which sounds incomplete, and a secondary phrase fulfills in its response. The longer the melody, the more of a story and dialogue can take place, as in an opera or musical.
There are additional elements that affect the expressiveness of each melody: the speed (tempo), the volume (dynamics), and technique (articulation - think short notes versus smooth and connected versus accented). Different instruments will also provide a variation in musical color, known as timbre: the human voice, piano, violin, tuba, oboe, synthesizer, etc.
The ability to both internalize melodies and be moved by them is quite powerful, so much so that there are moments in history where melodies have been banned. Take, for example, Jean Sibelius’ “Finlandia” - the unofficial anthem of Finland, once forbidden to be performed by the Russian Empire during the turn of the 20th Century. Performers kept changing the title to avoid censorship; it’s a fascinating story - additional information here:
Some tunes are so beloved and revered, composers utilize them in their own works to pay homage to other composers: Christopher Nolan’s film, Dunkirk, particularly comes to mind, in which Hans Zimmer references Sir Edward Elgar’s “Nimrod” variation during the climatic scene.
I mainly listened to classical recordings growing up, particularly older ones. While studying piano, I listened to a lot of solo artists. Often, they were an older, seasoned performer who would be humming along during their studio recording, most likely without realizing it. They were expressing the melody in such a focused manner, they did what came most naturally as a musician: singing it. They did this as it became most naturally: singing it. We've all found ourselves humming while doing other tasks. Melody is the part we like to hum and sing out - it is also what gets stuck in our heads!
Melodies, whether they are found in a symphony, a film, or your favorite station on the radio are what we repeatedly remember after listening to a piece of music. They are the instantaneous “thumbnail” identifiers that can allow us to say, “You like Simon & Garfunkel, too? Isn’t the Boxer a great song?”