ffmpeg audio to visualisation
The following command shows a video with a waveform of the corresponding audio:

ffmpeg -i input.mp4 -filter_complex "[0:a]showwaves=s=1280x720,format=yuv420p[vid]" -map "[vid]" -map 0:a -codec:v libx264 -crf 18 -preset fast -codec:a aac -strict -2 -b:a 192k output.mp4


I replaced avectorscope with showwaves: avectorscope is for showing the difference between stereo pairs.
Try showcqt,showfreqs,showspectrum for other visualization effects.