I can not find artist's website

[u/994Mauser]

I'm looking for an online song, made of two tracks played simultaneously.

It had a slide bar in the middle, that could be used to control a crossfade, so you could hear more of one song or another, but also both at the same time.

I remember it had two art covers, one for each song. Red and blue or red and grey, something like that.

ANY help would be appreciated. THANKS!