Permission for remixes?
Do artists (such as the Propellerheads or similar) need to gain permission to remix another artist’s song?
For example, Professional Widow by Tori Amos was not only remixed but appeared on the Boys for Pele album so obviously this was approved. But Fatboy Slim "remixed" I See You Baby by Groove Armada - so did he need permission to do that?
To release a remix that you have done on your own initiative, In most countries you will need to agree terms with the original artist's record company.
However, in many cases the remix artist is actually asked (and paid either a flat fee, or a percentage) by the original artist's record company to do the remix, allowing the song to gain the interest of sections of the market that the remix artist has specific expertise in.