Check out the aggressive growl he gets on "The Real Thing" from Sergio Mendes' The New Brasil '77 album. Any ideas on what he was playing or how he coaxed out that tone? The track is available on Rhapsody for any of you who have it.

Anthony Jackson interview:
Q: One increasingly prominent aspect of your playing is a muting technique involving your right-hand palm and either a pick or your thumb.

A...............As for the "palm mute with thumb," that seems to be much older. Around 1972, I began falling heavily under the sway of Latin music, and I became enamored of the old Ampeg Baby Bass. Although it sounded pretty awful in nearly every other context, in Latin music no other bass sound could touch it, and I wanted it. I wasn’t comfortable with the idea of playing an instrument with such a stylistically limited range—or perhaps I should just be honest and say that I was determined to force my instrument to give me the sound of the Baby Bass. One way or the other, thumb-and-palm emerged as a personal technique giving me what I hoped was a compatible and effective sound for Latin music. Over the years, I’ve gotten comfortable with it, and I feel confident using it in non-Latin situations as well, although the peculiar problems of coordination due to the non-standard right-hand position have taken a lot of effort to overcome.http://www.pgw.com/catalog/catalog.asp?DBKey=102&CatalogKey=191284&Action=View&Index=Page&Book=202224&Order=165