On Vinylmint, sound creators agree to upload only original artwork, so each designer owns the rights to their design submissions.
This is true until the contest holder chooses one of the sounds as the contest’s winner. Then, and only then, can the sound creators agree to transfer his or her rights to that particular sound to the contest holder.
The designer transfers their rights in the Sound Handover Stage, and once it’s done, the contest holder becomes owner of the rights to that sound.
If a designer creates several design concepts for one contest, but the contest only buys one of them, then all the unused sound concepts remain the property of the sound creator, unless they have opted in to the submit their sounds to the Vinylmint Library Partnership Program. The contest holder can, of course, negotiate with the sound creator for the transfer of rights to more than one of their designs.
If the contest holder does not buy a sound creator’s work, it remains the property of the Sound designer.