Hi. I've been posting a few 8-bit cover of songs on youtube, from Blotted Science and The Mars Volta. The covers of the latter band have been recognized by Youtube as being property of EMI music and stuff.

I'm wondering... are covers illegal or something?

If they aren't, then this is literally a cover: People tab the song out using their (incredible) ear, and a software (which is a musical instrument) is playing the song back. In this example, in 8-bit.

So... is this copyright infringement?