Example 6a is a riff from my FretDance (2003) album from a song called Road Less Travelled. On the original tune I use a drop-A tuned seven string guitar for some really heavy riffing. This type of slap-muting sounds very cool indeed on a drop-tuned guitar. Check the tune out on my website. Same thing here, start out by learning 6A, which is the riff without slap-technique.