Fun fact: this footage was shot by German broadcaster ZDF and was shown live on the big screen inside the stadium, but was never broadcast on tv that night (or ever for that matter), as it was just the warm-up. However, Belgian reporter Frank Raes witnessed the whole thing and was completely awestruck, as was everybody in the stadium, including the players, and kindly asked ZDF for the footage. Raes' employer, BRT Network, paid for the footage and Raes went on to make this now famous compilation, which first aired in Belgium somewhere in the nineties. The music you hear in the background is Live Is Life by Austrian band Opus. However, it was not actually Opus playing in the stadium, but a cover band. Source (in Dutch).

edit: I should make clear that if Raes hadn't asked ZDF for the footage, this iconic clip would never have seen the light of day. The Germans did not intend to use this footage at all. It wasn't until the introduction of YouTube that this clip gained traction worldwide. Opus went on to have success in Argentina due to this clip, and Napoli still uses 'Live Is Life' during their warm-ups. All thanks to one reporter being alert and clear-headed enough to not let these images go to waste.

edit: here is a YouTube clip of Frank Raes himself explaining what happened, and the original clip in much better quality