This is an amazing technique the genius that is Rocco Prestia came up with. The funky, muted tones he got were often down to this fretting hand technique. Check it out in this lesson.
By the way, if you're into Rocco and funk bass playing, you might be interested in my Funk Bass course.
This lesson and the example is from my book Complete Fingerstyle Bass Technique. Don't forget to scroll down to download the free TAB/notation and backing track.
Francis Rocco Prestia - Fingerstyle Funk TAB + Backing Track
Complete Fingerstyle Bass Technique is available on PDF, Kindle, and Paperback.
Some of the shapes and patterns I play in the video lesson come from soul, RnB, and blues. This lesson will be of help to you if you're into those styles. If you're not, you can learn a lot about bass playing from the patterns you use!