Watch the Upright Muting online guitar lesson by Jasper Mortier from 50 Blues Bass Licks You Must Know
I first became aware of this muting technique with the palm of your hand by the great bassplayer Joey Spampinato in the movie about Chuck Berry: Hail Hail Rock and Roll. He was one of Keith Richard's favorite bass players and for a reason! And it also looks like what Rolling Stones former bassplayer Bill Wyman often does. Muting with the palm of your hand also comes really natural when you play with a pick (also often used by Bill Wyman for instance). Overall muting is influenced by your choice of instrument and strings. I like flatwounds for instance, especially when they get older. Joey Spampinato and Bill Wyman both like shortscale basses. That also influences the kind of overtones and the sustain and punch. And if you play upright: the notes of an upright bass die out faster in general, due to the construction and the acoustic nature of the instrument. And it's strongly influenced by the type of strings (like gut strings), the type of instrument and the way of picking up the sound. So why did they mute in the early days of the electric bass? Maybe too much attack distorted the old tube amps and/or speakers, which didn't have that much power in those days. And the whole recording process had a more limited dynamic range than we have nowadays. So muting made it easier to record. You could consider this 'muting' a mechanical compressor, I guess. Foam was often hidden under the covers of a bass and came standard with the bass - like the Fenders from the 50-ies and 60-ies. Later people started taking those off. For examples of bassplayers using foam under the strings listen to Donald 'Duck' Dunn on a lot of the Stax recordings. Most of the Motown and LA session players like James Jamerson, Bob Babbitt and Carol Kaye also used foam.