A cover song is a new recording of a song that was previously composed, recorded, and released by someone else.
You own the new recording (your version), but the original composer(s) own the composition (lyrics, melody, and song structure).
Requirements for a Cover
For a recording to qualify as a cover, the following requirements must be met:
You must not change the song's lyrics. Not a single word.
You must not change the song's melody.
You must not modify the song's structure.
It should not sound similar to the original recording; this is known as a "sound-alike" recording.
Not Covers
If the new recording has modifications to the original lyrics or melody, it is not a cover; it is a derivative work. You need authorization from the publishers of the original song's composers.
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If the new recording contains samples or tracks from other recordings, you need authorization from the owner of the original recording to use it in your song.