Is it really impossible to isolate the vocal and the music clearly? if yes... what is this?
Isolated vocal only:
original:
I would imagine the remixer was provided with a vocal stem.
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In other words, yes, it is impossible, and the samples in the question were not separated after the fact. The vocal only track was obtained from the original multitrack recording in some way. Nov 4 '15 at 15:36
On very few occasions you may be able to extract the center track from a song cleanly, which is usually the vocals and basic instruments like drums which can be somewhat EQ-ed out. In this case, however, you may do what the remixing artist most likely did and find the stem on www.acapellas4u.co.uk where it is currently listed as an available acapella track. You just have to register (which is free).
If you can get an instrumental version or reproduce perfectly one of the version you still can substract voice from the track then perhaps try to use audio repair tools to make it clearer. Drums can be attenuated by accentuating drum attacks then attenuating global transients. I'm not sure you will get the best result but I guess these kind of technics can work if you only want samples from the song. Here is a link i've found on Youtube:
You could then use Audacity.