As a research site on the good (and bad) of the Sonic series, we couldn’t possibly let this one slip past us.
Russian Sonic site Sonic Scene posted what appears to be the music used in the very first trailer of the later ill-regarded Sonic The Hedgehog (2006). What’s special about all of this is the track was never used in game or, more over, released in any sort of auditory form aside from a trailer with off-mic noise.
But thanks to the efforts of Russian Sonic fan Mefiresu, he found a song that is strikingly similar to the audio used in the video. You can grab the near-five minute clip and listen for yourself right here.