= FFmpeg sound synthesis
{c}
Simple <sines> and variants:
* https://unix.stackexchange.com/questions/82112/stereo-tone-generator-for-linux/536860\#536860
* https://stackoverflow.com/questions/5109038/linux-sine-wave-audio-generator/57610684\#57610684
* https://superuser.com/questions/724391/how-to-generate-a-sine-wave-with-ffmpeg
* https://stackoverflow.com/questions/59551013/how-to-generate-stereo-sine-wave-using-ffmpeg-with-different-frequencies-for-eac/77730492\#77730492
2 second 1000 Hz:
``
ffmpeg -f lavfi -i "sine=f=1000:d=2" out.wav
``