What is Sound design?
Sound design is the craft of creating and shaping the individual sounds in a track — through synthesis, sampling, layering and effects processing — as opposed to composing the notes those sounds play. In techno, where tracks use few elements, sound design largely is the music.
A techno track might contain eight sounds total, which is why each one carries so much weight: the kick's texture, the rumble's movement and the percussion's character define the record more than its (often minimal) melodic content. Core sound design skills for the genre are subtractive synthesis (oscillator → filter → envelope), sampling and resampling, layering complementary sources, and effects chains — saturation, reverb, delay and modulation — used as instruments in their own right.