got an answer from ITMS :
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Dear Cyril,
Thank you for contacting the iTunes Store team.
We have researched the issue you reported and have verified that the artist intended the slow tempo. This song employs a special mixing technique. Songs that use this technique are called "chopped and screwed".
To learn more about the origins of the "Chopped and Screwed" mixing technique, please check out the Wikipedia entry:
http://en.wikipedia.org/wiki/Chopped_and_screwedIf you ever have a question about the version of the song you are about to purchase, please listen carefully to the song preview. To preview a song, double-click on the song or audio book in the iTunes Music Store and the preview will play.
When you listen to a song preview in the iTunes Music Store, you're listening to the actual song that is available for purchase. The song preview is not a separate file.
Sincerely,
Pierre,
The iTunes Music Store team
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