The late 1970s became filled with science-fiction films that started with the huge success of Star Wars.  Soon after, more films like Star Trek: The Motion Picture and to a certain extent, Superman: The Movie, would follow.  Another science-fiction film would follow as well, but within the realms of horror.

That film is Alien.

Directed by Ridley Scott, whose only other film he directed at the time was The Duellists, the movie had a simple premise, following a group of astronauts being terrorized by a carnivorous alien.  Its production design, atmosphere, and the creature, istelf, established the film's look and feel, and the character, Ripley, which starred unknown actress, Sigourney Weaver, became an established female heroine in the genre.

Another major part to Alien's success is the score by veteran composer, Jerry Goldsmith.

Prior to Alien, he wrote a plethora of film scores during the 70s, notably Patton, Capricorn One, The Omen, Logan's Run, and The Wind and the Lion.

He had written science-fiction scores before Alien, with his scores to Planet of the Apes and Logan's Run being the prime examples.

Around the same time he wrote Alien, he also written the score to Star Trek: The Motion Picture, which is a pretty great score.

However, he clashed more often with the director and the editor in Alien than in Star Trek: The Motion Picture.

This particular video goes into that detail:

(the music section starts at the 6:42 mark)

So, you can clearly see how the editor and the composer clashed in terms of style with the music.

Temp tracks can be a double-edged sword, since the director is more in tuned with the film with the temp tracks, rather than allowing the composer to write something that would not follow that temp track to the note.

If you ask me, it should be up to the composer to make the call on what should be written for the film.  They have the talent and the experience to come up with something that they feel is close to what they see on the film.

The composer who had such talent and creative control over his music is Bernard Herrmann.

Usually, everything goes his way.  He has an idea for what should go into the film.  If he can't agree with something with the director, he would leave.  It's for that reason he left Alfred Hitchcock during the production of Tom Curtain, since Hitchcock wanted a more pop-oriented soundtrack, which Herrmann believed didn't work for him.

For Goldsmith's case in Alien, I think it would, indeed, be more terrifying if it wasn't as obvious from the start.  You bring in your audience with some wonderful music, let it give you that sense of wonder, before someone gets their face hugged.  Build up the suspense and create that sense of dread.

To see the idea, here's the two different themes Goldsmith mentioned:

(Original theme)

(Film Version)

The original version had a certain grace to it.  It had some horror element, but it didn't bang you over the head with it.  Instead, it sounds more majestic, letting you feel more at peace than anything else.

The film's version is a lot more obvious with its intention, being very strange, horrific, and not having any sort of peace like the original did.

Plus, the tracks that they used as temp were ultimately placed in the film: a cue from Freud: The Secret Passion and Howard Hanson's Symphony No. 2 ("Romantic").

These cues are pretty good, but against Jerry Goldsmith's music for Alien, it screws up the continuity, since they are both thematically different.

Aside from that, this is an interesting score.  It has some cool ideas and give a sense of wonder to a horror film.  If there was a major complaint the score is that it's mostly an atmospheric score, not having a lot going on and mostly being more like filler music than having each cue do something that would catch your interest.

Ultimately, the score was released on various albums, with more recent ones having cues from Goldsmith's actual writing and recording.

If you want to hear what Goldsmith ultimately wanted for the film, give the albums a listen.