When people think of the Harry Potter films, they usually think at least in part of the score by the legendary John Williams. In terms of how memorable and challenging it is, “Hedwig's theme"is up there with"The Imperial March" from "Star Wars" or "He is a pirate" from the Pirates of the Caribbean movies, that anyone can memorize and hum along to in the moment. Regularly producing bangers like this, it should come as no surprise that John Williams has earned over 50 Academy Award nominations throughout his career.

So it's a little surprising that Williams wasn't actually there for most of the Harry Potter movies. The Goblet of Fire soundtrack was composed by Patrick Doyle, Order of the Phoenix and Half-Blood Prince were composed by Nicholas Hooper, and both Deathly Hallows films were composed by Alexandre Desplat. A keen ear will pick up on these changes over the course of the series, but given how much the score from the first film would be reused and adapted in later films, it's easy to assume that Williams was there all along.

In a 2010 interviewproducer David Heyman explained why Williams didn't return for Deathly Hallows, even though they definitely wanted him back. “We wanted to work with John, but John's schedule wouldn't allow it,” he said, later adding: “We asked him around the time of (film) six. "We actually talked to him the whole way (about coming back eventually), but his schedule wouldn't allow it. ... He tried to work his schedule to try to accommodate it, but it just wasn't possible."

Much like the reasoning behind Williams' absence from returning to Deathly Hallows, he left the series after Prisoner of Azkaban in part because he was too busy. He had the epic Star Wars: Episode III — Revenge of the Sith to compose around the same time, not to mention War of the Worlds and Munich. And even though Williams' name is attached to "Camber of Secrets," he wasn't as involved in it as he was in the first film. Like composer William Ross, who worked extensively on Chamber of Secrets, explained in a 2013 interview:

“(Williams) also explained that there could be a scheduling conflict that could somehow affect his participation in the second film. the new film he intended to use and adapt the themes from the first Potter score John asked me if I would be interested in taking that original material and adapting it to work in the context of the new film way to know how much work would require that because he hadn't seen the film yet and didn't know at the time how much the scheduling conflict would be a factor."

If you were wondering why the Camber of Secrets soundtrack feels a little lower than the magic of the first film - including that part of the Quidditch match where the score appears it seems a little too similar to the score in the Star Wars prequels. - this is part of why. Williams, who was busy composing the a wonderful Spielberg film "Catch Me If You Can" couldn't devote as much time to the first "Potter" sequel.

The good news is that, although Williams never returned to the series after Prisoner of Azkaban, that third film served as a quasi-comeback for him. "Camber of Secrets" may have been a slight step down, but the "Prisoner of Azkaban" score is by far the best of the entire series. (Which makes sense, given that it's also best movie of the series overall.) "Buckbeak's Flight" and "A Window to the Past" were not only some of his best work, they were also quite original, not just a continuation of the earlier Potter music. The entire score for Azkaban had a darker, more gothic feel, complementing the film's more mature themes.

Although Williams only composed two and a half of the franchise's eight films, he still easily overshadows all composers to come after. That's largely a result of it being Williams who nailed the tone of the series from day one, providing a Harry Potter blueprint for all of its successors to at least partially work with.

It also helps that a big theme of the film is nostalgia; later series Harry longs for the days when his life at Hogwarts was relatively simple, and of course every adult in the series pines for the times when Lily and James Potter were still alive and well. When a later Harry Potter film wanted to be nostalgic, the easiest way to capture that feeling was to reuse iconic themes from the first film.

When asked about this, "Deathly Hallows" director David Yates explain his thought process behind knowing when to bring back "Hedwig's Theme": "Anything that feels nostalgic or in some way reflective of the past. That's when we used it," he said. Of course, some iteration or variation of Hedwig's Theme will be used in every Harry Potter film. In a lesser franchise, this might seem lazy, but in this case, it's hard to find a Potterhead who would ever complain.