You can use any asset (music, code, picture etc.) made by someone else only if you have explicit permission from the original creator to do so, or if the asset was released under a permissive license such as Creative Commons. In any other case, using such assets is prohibited and may result in disqualification. Though in case of song covers, if this is what you're asking about in particular - if the original song is copyrighted, then using a music file that's a cover of it will also most likely get the entry disqualified.
Also, please keep in mind that any assets made with generative AI are not allowed, even if they were produced by someone else and released as free to use or under a permissive license.