I used two layers of diverging paper stripes that will rub against each other when being rotated (and thus creating sound) to represent the audio. The upper layer was printed in CMU plaid as to represent context of bagpipe marching performance ––the kilts for pipers have similar pattern and the lower layer was colored in black as a dark and relatively solemn background. (Yet, in the outcome, the color of plaid seems too dark and the black makes it look even darker, which was a bad choice = =)