Best practices for creating and uploading a track composed with someone else
Everyone who worked on those tracks owns part of the copyright for them, and you'll need to have everyone's approval before you can upload them to SoundCloud.
If you have written the lyrics, you own the copyright to them. However, if you did not create the beat or instrumental backing track, then somebody else owns the copyright in that (and vice versa). You would need their explicit permission before uploading the track to your profile and the other party can request that its publication shall be blocked if you do not have their permission.