Here are the situations in which you typically need a license for each of these scenarios:

Samples:

1. Using copyrighted material: When incorporating samples of copyrighted music, sound recordings, or other audio elements into your own music, you generally need a license from the copyright owner or their authorized representative. This applies even to brief snippets of copyrighted songs.
2. Fair use exception: In some cases, limited use of copyrighted material may qualify as "fair use" under copyright law. However, fair use is a complex legal concept and should be assessed on a case-by-case basis. Consulting with a legal professional is advisable to determine if your use qualifies as fair use.

Cover Songs:

1. Creating a cover: When recording and releasing a cover version of a copyrighted song (performing someone else's song in your style), you typically need to obtain a mechanical license. This license grants you the rights to reproduce and distribute the cover song. You can obtain a cover license here.

Remixes:

1. Creating a remix: If you are creating a remix of a copyrighted song (altering or reimagining an existing song), you typically need permission from the copyright owner or their authorized representative. This often involves obtaining both a mechanical license and a master use license (for the use of the original recording).
2. Sampling in remixes: If your remix includes samples of the original recording, you must clear those samples with the appropriate rights holders.