| It's called double-thumbing, you basically modify your slap motion to resemble alternate picking (like on a guitar).
Instead of letting your thumb bounce off the string, you "go through" the string, stop at the next one, and then move back up.
Victor Wooten, Adam Nitti, Ray Riendeau, Marcus Miller and lots of others use that technique too.
__________________ "El sueno de la razon produce monstruos." "The sleep of reason brings forth monsters."
Francisco
Goya |