Game Audio
Overall vibe of the auditory aesthetic. You may want to additionally define any leitmotifs in use.
Theory
Is there a fixed mode or scale? Any rhythmic motifs? Leitmotif? Define them here. If you don't know, feel free to erase this section and just play with the rest.
Sound Palette / Instrumentation
What are you going for with the instrumentation? Dark, bassy tones? Happy, high-pitched tones?
Even electronically synthesized instruments can use a well-grounded basis. What real instruments do you want to base your palette on? Where is the emphasis, which instruments (if any) will carry the focus?
Is there an existing song or two you want to draw from?
Stylistic Attributes / Effects
Any particular musical/auditory motifs (signature phrases/effects) you're planning to incorporate?
Does the game have a specific 'theme' you want to reuse throughout the soundtrack?
Will you use musical cues to draw attention to certain parts of the game?
Efects
What post-processing techniques are you going to need? Cross-fading? Reverberation? Filters?