From Hellgatewiki.com

The audio elements of Hellgate: London are important aspects of the game. They are not essential; sound cues aren't required to defeat any section of the game, but hearing the monsters moving around you and enjoying the NPC dialogues and monster grunts and snarls and the music itself is a big part of the fun.

Hellgate: London uses all the newest technology for sound, with 3d surround, voice communication support, and more.

Sound Effects

Hellgate: London has 3d surround sound, of course, and it's quite effective when you hear the game with good headphones. Monsters are audible in every direction, and ambient noises such as the low hum of machinery or the creak of armor are very real.

In addition to the technology, there are some really good monster noises. Players who have gotten early play time report that almost every monster has a distinctive moan or squeak or howl. Zombies slobber and snarl and gibber in almost disturbing fashion, and larger, more menacing monsters sound... like large and menacing monsters.

Other sound effects are also noticeable. There's an impressive, triumphant blare of horns when your character levels up or completes a quest, that many players have reported enjoying, especially as it combines with a heavenly light and shower of sparks to reward you for your level up.

Dialogue

There is quite a bit of spoken dialogue in Hellgate: London, though not as much as some RPGs offer, since spoken dialogue adds complications when the game is localized into foreign languages, and Hellgate: London is being translated into numerous languages. NPCs generally have verbal greetings, and some speak long blocks of words, though most of that sort of dialogue is presented through text that you can read or just skip right past if you prefer. In addition to their quest-related conversation, the NPCs have lots of funny or wacky catch phrases that they shout at you every time you meet.

The train-repairing tech smith you meet early in Covent Garden Station was the funniest and weirdest NPC I found in the game. He makes all sorts of brainless and worshipful comments to your character, and does them in a funny voice for bonus effect. Several times I clicked on him while running past, just to see if there was any update on the quest he had me on. There wasn't, and as I ran away he'd shout after me (his voice fading as I moved thanks to the headphones and 3d sound), "Ahhwhooo! That was the best conversation I've ever had in my life!"
--Flux, Mega Community Day Report, May 2007 (Forum registration required to read full report.)

Music

The music for Hellgate: London is rock-oriented with some electronic and industrial aspects to it.

"We have two separate groups of composers working on all-original music for the game. The mood we have been striving for is an eclectic mix of both modern and classic sounds with a post-industrial edge. The music in the first Blur cinematic was a good launching point, and represents the genesis of our ideas in regards to the music for the game. We are also doing some things compositionally and technologically in how the music is being presented to the player that accentuates the game play experience.

"This has been a real challenge for the composers, but the results so far have been great. Basically, the music is written, performed and integrated to support and reflect what is happening in the game at any point in time. This also means that the music and the sound effects are very conscious of each other from a mixing standpoint, making for a very complex and rewarding soundscape."
--Bill Roper, February 2006

Much of the Hellgate:London music is being created by Sonic Mayhem, a studio best known for their work on the music of Quake II and Quake III. Their official site does not list Hellgate: London as an ongoing project, but HGL is mentioned prominently on their myspace site. On both Sonic Mayhem pages you can download a number of mp3s of their work, though none from Hellgate: London are yet available.

Music Samples

If you want to hear some samples, the largest chunk of Hellgate: London music yet released can be heard in the 2005 E3 cinematic. That music was created specially for the cinematic, but it's fairly-representative of the overall music in the game. Two more samples were posted in a two page article on 1up.com in early 2007. They play streaming through the pages if you load here and here.

More sample tracks may be released before the game, but Flagship hasn't said anything about it, yet.