Samples? Only with the copyright holders permission!!!
If you sample an Abba track you need the permission of the copyright holder to the song (the publisher), and permission of the copyright holder to the version of the song from the recording from which you are sampling (the label). Either party can reject the request and not grant you the right to create a derivative work.
Without the approval from the copyright holders you cannot upload the music.
A derivative work?
A derivative work is when you decide to record the sample yourself instead of taking a sample from a preexisting track.
A derivative work is a re-recording of someone else's original work (for example you do a recording of yourself doing someone else's riff instead av sampling the recording of the riff). In this case you need the permission of the copyright holder of the song (publisher) but not not the recording (label). But you still need permission!