Legal Question in Intellectual Property in New York

If the uploader has the right to distribute the music (the upload is a distribution, even if the work is not then shared), then there's no problem; if the uploader does not have that right, the uploader has infringed the copyrights associated with the music using this website as the vehicle.

You may not actually know whether the uploader infringes copyright, but it's a pretty safe bet that they do, so your claim to ignorance would not be reasonable.

THIS POST CONTAINS GENERAL INFORMATION AND IS INTENDED FOR ENTERTAINMENT PURPOSES ONLY. IT DOES NOT CONSTITUTE LEGAL ADVICE, NOR DOES IT CREATE ANY ATTORNEY-CLIENT RELATIONSHIP. FOR LEGAL ADVICE ON YOUR PARTICULAR MATTER, CONSULT YOUR ATTORNEY.