Lyrics aside, there is quite a bit of study out here on the effect of rythym and percussion. A lot of it has roots directly to African Voodoo and the trance states produced with drums opening a subconscious portal for spirits. The rythym of stringed instruments also has a similar effect. Jimmy Page is a master of the guitar riff and it is a major part of the Led Zeppelin sound (along with the heavy drum sound he produced for their records) and all metal music which he heavily influenced. Page was a total devotee of Crowley, practicing black magik and actually lives in his old castle. Doesn't get any creepier than that!