Jay Weinland began by exploring the transition from the Xbox to the Xbox 360. Halo 3 was their first title for the platform, and as a result they made some substantial changes to their workflow. Software tools they'd put in place for the previous games continued to be developed, improving their tools and adding options. They also had the chance to make use of technology advances when moving from the original console to the 360.
The console's multi-thread processor was divvied up among the game systems, and almost an entire two threads of the chip were dedicated to audio elements. There is also an onboard audio chip, which gives the developers access to "free decodes" of audio data. As a result some 320 independent voices can be piped through the system at the same time. The problem they were running into was that they couldn't make best use of the system because of rendering issues. They ended up actually using "32 mono, 32 stereo, 12 4.0 and 8 5.1 voices" over the course of the game to ensure that players had a quality experience.
To keep us interested Weinland then went on to play two clips from Halo 3 audio sessions. First we have Adam Baldwin's riff on a speech from Full Metal Jacket:
Then we have the angry, ranty stylings of Debra Wilson:
After the clips the team went on to make use of a great big room (called the "stripey room") inside the game engine to show off the audio fading system they use. Close-up sounds have a lot of detail, but as the source of a sound fades into the distance the quality decreases until the sound is just a mono clip. The room in the game is made of up striated bands consisting of every material in the game, to ensure that the sound designers can judge aural elements against wood, metal, etc.
The change was quite striking, as up close you'd hear elements like the bullets in the chamber / shell casings hitting the ground. Far off, the mono sound would fade into the background noise often heard as window dressing in the multiplayer maps. They also dropped a Mongoose vehicle into the room to show what the change in quality sounded like for consistent noises - a marked improvement over previous Bungie titles.
Composer Martin O'Donnell, well known for his work on the Halo
soundtrack, finished out the session by demoing his composition software. Essentially he and Mike Salvatore create musical pieces than can be formed into a cohesive whole by simply overlapping and interlocking pieces. By setting a drumbeat going, or a single high note, he sets a mood that can then be modified through the addition of other compositional elements.
This software allows for the level of variety needed in a videogame environment, ensuring that (except when it's dramatically appropriate) the musical landscape will be a varied as the firefights you'll encounter in-game. O'Donnell's cardinal rule is "do no annoying", and by mixing and matching in the studio (and on the fly) the composers can create all new experiences for players that enjoy the dramatic series music.