I don't think I consider songs to have a canonical rendition. However, I might consider a rendition of "Canzonetta Sull'Aria" by Britney Spears and Madonna to b

I don't think I consider songs to have a canonical rendition. However, I might consider a rendition of "Canzonetta Sull'Aria" by Britney Spears and Madonna to be 'incorrect', and this has less to do with their image than with their voices. By all means, one should sing old songs, and for many purposes remember Chesterton's dictum that 'anything worth doing is worth doing badly'. But if one is going to market an album of X sings Y, it is well if X actually can sing Y close to tune.