Best practices for uploading someone else's track
Buying or downloading a track doesn’t necessarily give you the right to upload it to an online platform or to make it available to a wider audience. As you may know it is still possible to share private tracks with other listeners. Remember to only upload content, both publicly and privately, that you own the copyright to or that you have the necessary rights holder permission to make a copy of and publish online.
Also, crediting the original artists on their track does give you legal permission to post it online. You'll still need explicit permission from all relevant copyright owners before you can upload someone else’s track to your profile, use it in a DJ mix or create any kind of derivative work from it (such as a mashup, remix, etc).
Please note: Based on current copyright legislation, you can only upload content to your account that you own the copyrights for or have the appropriate licenses to upload and make it available online from all relevant copyright owners.
If you created a derivative work based on tracks that you have downloaded or found from other sources online - you would always need that content’s creator’s permission to upload it to your account. Please also bear in mind that crediting the original creator and mentioning that the track has been used for non-commercial purposes is not sufficient.