I can add a solo-instrument part to an arrangement without getting permission since it is not altering the original song.
INCORRECT
Only the owner of a copyrighted work is allowed to create new works that are “based” on a pre-existing work. Copyright law describes this derivative work as: “...a work based upon one or more preexisting works, such as a translation, musical arrangement, dramatization, fictionalization, motion picture version, sound recording, art reproduction, abridgment, condensation, or any other form in which a work may be recast, transformed, or adapted.” You must seek permission from the copyright holder to publish a derivative work.
CORRECT
Only the owner of a copyrighted work is allowed to create new works that are “based” on a pre-existing work. Copyright law describes this derivative work as: “...a work based upon one or more preexisting works, such as a translation, musical arrangement, dramatization, fictionalization, motion picture version, sound recording, art reproduction, abridgment, condensation, or any other form in which a work may be recast, transformed, or adapted.” You must seek permission from the copyright holder to publish a derivative work.
