MetaSynth is a sound design and music production tool developed by U&I Software for the Macintosh operating system, that allows the creation of sound from images. It was most notably used on The Matrix, but has also appeared on the electronic artist Aphex Twin's single "Windowlicker" in the title track and the B-side track "ΔMi−1 = −αΣn=1NDi[n][Σj∈C[i]Fji[n − 1] + Fexti[n−1]]".