Watch the Right Hand Muting online guitar lesson by Stu Hamm from Stu Hamm U: Slap Bass

Another way to add tonal color to your thumb playing is to use the heel of your right hand to mute the string. This will give you a punchy but not sustained tone, not unlike the sound made popular by bass greats Paul McCartney and Carole Kaye.

Notice how the tone created with this technique is completely different than when we use our forearm to mute the string.