They’re the unsung heroes of Hollywood, those whose job it is to stop your heart, steal your breath and leave you gasping for more – and the chances are, you’ve barely given their work a second thought. For this is the world of trailer music: an industry few people know exists, producing scores heard every day by millions.

“People just assume that the music in the trailer is from the film,” says the veteran TV and film composerJohn Beal, talking from his LA home. “That was the case a long time ago, although the music was taken from other films instead. Back when I started, only the occasional trailer was actually scored. The process has changed a lot since then.”

He should know. Beal was the first of his kind: a composer creating original scores for film trailers. “I realised the trailer was not being served as well as the picture was,” he says. In 1979, he was given the chance to put that right, when he scored the trailer for Skatetown, USA, Patrick Swayze‘s debut. Since then, Beal has been the man behind the music for more than 2,000 trailers – scoring everything fromThe Matrix to Mean Girls. “After 30 years of doing this, the soundtrack in my head as I’m doing the groceries is a lot more dramatic than other people’s,” he says. “I live in a constant state of hyperbole.”

It’s easy to see why. The art of scoring a trailer requires not only a certain style of thinking, but an entirely different approach to composition. Trailer scores are commissioned by production companies via “trailer houses”, which produce the final edit. They typically last two minutes and are split into three parts: beginning, middle and end, usually all containing different pieces and styles of music. The goal is to produce a heavily briefed, tightly wound and meticulously edited piece of work in which every second counts. “To write something that develops so fully and extremely in two minutes,” Beal says, “is something a lot of composers, including guys who are way better than I am when it comes to long-form film scores, just can’t do.”

Even so, times have changed. Production companies are no longer keen to commission original pieces for trailers, preferring instead to opt for music that they know has worked for other movies. Says Beal: “The brief I usually get these days is, ‘As little as possible in terms of budget, as big a sound as possible, and just like something that somebody else did but different enough to not get us sued.’ Mostly I’ll be asked to emulate composers such as John Williams, James Horner’s Aliens or to do something with the same epic feel of Carmina Burana.” Of course, the issue of production companies trying to dodge licensing fees for non-original music – which can go as high as $75,000 – creates problems for composers told to all but recreate that music. “There’s only so many different versions of something you can do,” Beal says.

In a way, the fall in demand for originality is understandable: on projects worth millions of dollars, why take a risk on something new that might not work? Then again, it could be seen as a snapshot of a wider picture: of a conservative, corporate culture that has seeped into every crevice of the Hollywood machine – the same culture that insists on endless sequels and remakes. “A lot of head of studios have come from marketing,” Beal says. “Executives who don’t really understand the art of film-making, but understand the art of film selling.”

It is perhaps because of this aversion to risk that one area of the trailer music industry is thriving: music library companies. These are firms who build up a varied, high-quality repertoire of orchestral music that can be licensed out. Because of their greater size and resources, these companies – unlike composers such as Beal who work alone – can usually record their music with a full orchestra as opposed to synthesisers and samplers, which helps their catalogue stand out. It’s a difference that Beal describes as akin to “writing a script and getting a top Hollywood star to act, as opposed to yourself”.

“It’s a gamble,” says Jeff Fayman, co-owner of Immediate Music, a trailer library he runs in conjunction with his partner, Yoav Goren. “There’s a chance that, for all the thousands of dollars we spend on hiring out Abbey Road with an orchestra and all the months we spend in pre-production, post-production, editing and mixing, none of the music we make will ever be licensed. Then again, we are fortunate that we can get up in the morning, get an idea and say: ‘Wow, let’s do some music like this.’ From start to finish, it’s 100% our inspiration and motivation. And if we like it, we’re sure our clients will, too.”

Immediate Music is the biggest trailer library in LA, having worked on campaigns for Spider-Man 2 (which featured in its trailer the grandiose, choir-soaked Lacrimosa, a piece that is only a breath away from Carmina Burana in places) and the last Harry Potter film. It is also the most progressive. With the rise of the internet, trailer libraries started to despair over their work being uploaded and shared online – after all, exclusivity is key to their business. Immediate, however, embraced this by releasing a commercial album called Trailerhead, and put together a band, Globus, which performed at Wembley Arena in 2006. Soon after, another trailer library, Two Steps from Hell – whose music has been used in TV shows such as The X Factor and Doctor Who – followed suit with its own album, Invincible. The success of these two ventures with the paying public is a testament to how far trailer music has come from the days when any old noise would do to promote a film.

Yet isn’t the idea of having creative freedom, making art and winning a fervent fanbase in the course of creating what is, essentially, music designed to advertise rather strange? Not at all, Fayman says: “There’s a difference between selling it as a commodity and putting out music you genuinely believe in. I believe trailers are about provoking an emotional response from people, and that’s why I think it’s been taken to the levels it has. As an artist, I believe that there is nothing more rewarding than to create something you believe in and that people also respond to. And isn’t that what music is all about? To us it isn’t trailer music; it’s just music.”

This piece first appeared in The Guardian in August 2011.