I don't understand what you mean by cover, like as properly playing the music on the sheet or arranging the music on something different from its original intentions?

>>788 I think he means how much you can change the original tune before it starts sounding like a different song. To answer OP's question >>787 from a newb's point of view the main three aspects are: >A: the key the song is in Obviously if you want to rearrange it you'll have to play it in the same key or in a parallel one I believe that's what they're called please don't shoot me I started music theory just recently >B: the main motif Every song has a main part that makes people go "Ah ha it's THAT song" >C: the memorable parts Like point B, except it's other stuff, you just know them when you hear them. I figure if you left those 3 things mostly intact then you could tie together whatever other addition, changes and embellishments of yours without drifting too far from the original idea.