DJ Snake - 'Bird Machine feat. Alesia':
This release was done through Jeffree's, a sub-label of Mad Decent. Their business model is covered in this Billboard article but to paraphrase it briefly: Jeffree's is used by Mad Decent to sign one-off track deals with producers which is then release it to the public for free. If the track gets some buzz they will start selling it. It's a win-win proposition for the producer, label, and fan which has helped launch the career of Baauer with his Jeffree's backed hit, 'Harlem Shake'.
Be sure to bookmark the Jeffree's site to download future releases for free.