FYI... When watching TV, the surround speakers are already in “full mode”. The audio that is played out of the surround speakers is determined by the source. If the source is multichannel audio like Dolby Digital 5.1 or multichannel PCM 5.1, the rear speakers will play the left and right rear surround channels from the audio track at FULL volume. If the source is stereo 2.0 audio, which I am assuming is what you are referring to when watching “music videos”, the rear speakers will perform an audio up-mix of the stereo signal to create a simulated surround sound.

So what you are actually requesting is a “full mode” only from stereo audio sources when watching TV.

There are music videos with 5.1 audio tracks too and you wouldn’t want the surrounds to play the audio in the same “full mode” you are requesting because it would actually take away from the intended 5.1 audio mix.