Using Groove Levels to Set the Mood

In Worms Blast, the player must keep his character from being squashed between the water under his boat and the blocks overhead. If the water level rises too high, the space above the character's head will narrow, and he will soon find himself in trouble. I wanted to use this in the music, to let the distance between the water and the overhead blocks determine a "stress factor" or "danger level," which would be reflected in the music.

For each of my four different in-game music projects, I wrote about six different main musical parts. I then created five different versions of each of these parts with different intensities. For example, I had an eight-bar pattern called "main melodic part A — level 1." It was calm, laid-back, almost cozy. I copied it to a new pattern and called it "main melodic part A — level 2." In this version I introduced a few more drum sounds, but it was still pretty laid-back. I kept doing this until I had five different "mixes" of the same pattern. The fifth one was very intense, with drums playing double-time and some distorted instruments playing busy melodies along with the main melody.

I then assigned groove levels to each of these patterns 11 through 20, 21 through 40, 41 through 60, and 61 through 80. I asked the game programmer to use the distance between the water and the overhead landscape to generate a number between 11 and 80. This number fed into the DirectMusic engine as a groove level. With this model in place, whenever the water gradually sank or rose or the landscape overhead gradually caved in or withdrew, representative patterns would play. The end result was that the music had a higher stress level, according to how much danger the player's character was in.

I composed a few more patterns and assigned them to groove levels one through ten. These patterns were very low intensity, basically just a subdued rhythm with a few occasional notes. I called this "pause music" and asked the game programmer to set a groove level of one when the game was in Pause mode. Pausing the game causes the music to change to "pause music," while keeping a steady rhythm going. This worked really well; it sounded natural, slick, and cool.

In addition to the different pattern intensities, we also implemented slow, subtle changes to the master tempo, which was tied to the groove level. As the distance between the water and the blocks decreased, the groove level increased and so did the tempo. We created a tempo scale from about 100 percent to about 120 percent of the original tempo, as set in the Segments, and had the tempo change by one percent at a time. This combined with the different patterns with varying intensity levels to further enhance the connection between the stress level in the game and the stress level in the music.