This is a video of the crude concept running on my SFML port of TV_out. Audio signal is emulated by a 8kHz generated sample. Due to a bad bug in ALSA lib, refreshing sound buffer dynamically is broken = reason why sound is cut when synthesis parameters are changed. This will not be an issue on the Arduino.
The sound & video quality is horrible. Sorry.
UPDATE:
Unfortunatey, on the Arduino, I am getting interference that is messing up the tv signal... I'll need to troubleshoot that.