It's alright. Let me re-phrase.
I want to slow down an MP3 from my downloads folder, and slow it down so the pitch is effected as well, generating a lower pitch effect. It's like with slow-mo videos, where voices sound very deep and the video is slowed down. I want to do something similar. I want to slow down music so the pitch falls. Most websites just stretch out the music, therefore not changing the pitch.