Reply to How to name remixes

I read on Laidback Luke's community that if you remix a track, without the artists permission, then you have to call it a bootleg, not a remix. He said remixes are only allowed to be called that when the artist has given you permission to 'officially' do it.

So my question is this. If i make a track and use the melody an old 80's song used, but never officially sampled the song, just played the same notes/keys in my synths etc do I need to credit the song, or call it a bootleg of the song who's melody i used?