In an interview he said he used to be a very good slapper, but since Flea and the peppers came out before them he gave it up. Later he learned that James Jamerson only used one finger so he learned how to play all of his bass lines with only one finger. He supposedly did something to his pups in his J bass to make them sound better and I believe it, as he picked them up after he smashed it at one of his concerts. As far as I know he also has a clean tone through one 8x10, then adds 2 levels of distortion each through half an 8x10, depending on how dirty he wants. I know the distortion comment doesn't have anything to do with your question, but it is still good to know, IMHO. Cheers.