The Musical Form

Form, in a nonlinear piece of music, abides by the same basic principles as linear music. Dynamics, harmony, orchestration, and the arc of the form are critical elements for any composition. Linear music, however, follows a singular path created by the composer, while nonlinear or adaptive music chooses one of many potential paths. This does not mean that adaptive music is formless. Its form lies within the boundaries set for the music. Creating these boundaries presents a new set of challenges for game composers.

For example, each potential outcome must make sense musically and adhere to the overall consistency of the piece. It is important for an adaptive piece of music to adhere to an overarching form, despite its many paths. The composer builds a musical structure in which the adaptive elements are contained. For example, a snowflake has a form that describes its basic elements — size, temperature, weight, and its crystalline form. Every snowflake differs slightly, yet they are all snowflakes. Adaptive music functions in this way.

The overarching form of Russian Squares is one of increasing intensity. Playing all of the music cells (DirectMusic patterns) sequentially results in a gradual building of musical elements, yet the performances that the gameplay produces vary greatly. The adaptive element of the gameplay provides the dynamic ebb and flow of music, while the instrument-level variation adds further nonlinearity. The form takes into account the fact that the music cells will not occur sequentially but will slide up and down the many groove levels.

Each groove level/pattern usually has one or two musical differences from its closest neighbor. That difference is an instrument addition/subtraction, an instrument change, a chord change, or a rhythmic shift. We arranged them in such a way that the music gradually moves from one large musical idea to another over the course of several groove levels. This gave the music a sense of form.

The tempo of each composition remains constant. We scrapped the whole idea of tempo changes for a couple of reasons. First, electronica does not usually feature gradual accelerando as a part of the form, so it sounded ridiculous. Second, it added some technical hurdles given our DirectMusic approach. The game would have to call tempo changes directly (with "increase tempo" or "decrease tempo" calls) or via controlling secondary Segments, which adds another adaptive design layer. Each style/pattern would need to function well within a range of tempos, and some of the DLS banks (i.e. drum grooves) were built around a specific tempo. We kept this aspect simple by having only one tempo per composition. To prevent it from sounding static, we used tricks such as rhythmic modulation to increase the music's sense of pulse. For example, the rhythm changes dramatically over five groove levels in Spin Cycle. The score achieves this change by introducing the new rhythm in one groove level and then gradually emphasizing it (while de-emphasizing the old rhythm) over the course of the next several groove levels. Each player experiences the shift at a different rate, depending on how well they play!