Speed reducer

Hi,
I'm practicing guitar and drums and I often use Deezer to find and learn new songs. But Deezer could be a better platform for musicians by proposing a speed reducer which don't change the pitch of the song. This kind of tool already exist but needs the MP3 file of the song which you can get with a CD or less legally... This can be combine with a loop tool, to repeat a specific part of a song with, as a solo.
Hope my propositions will get attention,
Musically