Makes a lot of sense, I guess they used the ubiquitous black plug for rear speakers jack...

Thx for link and explanation

> The WAV file has four channels of sound, the graphics (X and Y) are controlled
> by the front stereo channels, and the music is provided by the "rear" two stereo
> channels.
> A trick, but a pretty neat one :)
>
>
> [download a life]
>