As you know, Tom Morello makes lot's of sound effects with his guitar. One of them being a scratching noise which was influenced by the sound of DJ's. Anyway to do it (good) you need a two pick up guitar with two tone nobs and two volume nobs. Well tone nobs really don't matter, only volume nobs. You also need a switch(I forgot what its called lol, you know it changes which pickup(s) your using). It has to be the ones that only has two, Treble and Rhythm. So rub your hand across the strings in the area where you would pick and also a little bit near the end of the neck, and with your other hand constantly switch the "switch", w/e its called lol. I know he uses pedals as well, but I'm not sure what they are. There are videos on youtube of him teaching you how to do it, and he tells you what pedals he uses.