COMPRESSING...

Ok i tried searching for this but didnt come up with much. can some one please just explain the basics of compression to me. I want my beats to have that dirty grimey sound. First what is the point of compression? Second should i compress my samples before even entering them into the mpc or should i do this after my song is finnished. And finally whats a good program to use to compress. Someone please help!
Thanks

compression is basically lowering peaks and raising valleys in a sound wave. when done correctly it can allow your wave to be louder without clipping, as well as smoothing out large variations, like for example boosting a quiet fingerpicked quitar part and lowering a loud shreddy part so they come out at a similar level. for something like vocals, with a large dynamic range, compression can be pretty important. but badly used compression can suck the life out of sounds and beats so its important to understand and be careful of.

Try reading this article for an interesting discussion of what can go wrong with compression, as well as for the nice pictorial representations. you should find it informative.

http://www.prorec.com/prorec/articles.nsf/articles/8A133F52D0FD71AB86256C2E005DAF1C

Thanks for the link
But im still a little confused. What is a good program/software to use for compressing sounds? Also when shoul di compress sounds? should i compress my samples before loading them into the MPC of compress my finishes song after tracking and recording it to my pc?