You could start by jamming a piece of foam strip
about 1" x 1" x 5" long underneath in between the
body and your strings right up at the bridge.

Alternatively/additionally you use a mute
technique with your right and hand resting the
back of the hand on the strings to provide the
mute whilst using your thumb for the plucking.

Oh...and throw away that pick

Mo

I have seen older electric basses that had foam attached, or had a foam mute with a lever on it so it could be engaged or disengaged by the bassist.

Those MMSR Classics have that feature. I tried a Ray out
once and it seemed kind of a PITA to mess with if you're
planning on switching between songs. Rics had them too IIR.

Rics had them too IIR

You do recall correctly. They sounded good but were completely impractical to use unless all your songs needed a mute.

It took so long to tighten the screws and adjust you could have played 3 songs. I never understood why it couldn't have been lever operated. That would be a simple engineering task.

The foam thing is a good idea. Also consider plucking the
strings up around the 12th fret and end of the fretboard. I've
experimented with this a little and it seems to produce a little
"wool".

There are a lot of technological changes from then
to now that contributed to that sound. Bass
strings were flat wound and quite 'dead' compared
to today's strings even flat wounds. Fender
basses had foam mutes under the bridge covers that
were designed to control the attack and sustain to
be more like an upright. Amps had much less
power, less treble and were tube so they added a
lot of warmth and a softer attack than
contemporary amps. Players generally played
between the neck and pickup instead of over or
behind the pickup and used a much softer attack,
some even used picks or felt picks.
With all of that in mind there are several things
i've done to cop that tone: use a bass with old
strings, put a soft foam mute under the strings,
reduce the input gain on amp or pre-amp, reduce
treble on amp or turn bass tone control down, play
softly with fingers or thumb close to the neck.
These days I mainly play softly close to the neck
and pull up a patch on my effx set to simulate
that sound.

All great ideas to get 'that thumping sound' Brad. I'd like to add my favorite, use a low-pass filter and set the cut-off where desired. That works great to add thump.

That is part of the secret for sure, it's a patch
using a slightly warm SVT model and the lo pass set
about 2k and a touch of room verb, 'Motown Jazz' on
my cheet sheat.

a slightly warm SVT model and the lo pass set
about 2k and a touch of room verb

That sounds like a great tone. Anything Motown sounds good to my ears. You just can't argue with some of the greatest bassists ever.

All the above ideas are good ones. My fav has been
mentioned, which is to pluck the strings at around
the 12th to the 20th fret.

thank y'all for the feedback.

flat wound strings and a felt pick. Don

Felt pick!!! Sir, Carole Kay will hunt you down and cut your
heart out with a spoon for a remark like that! Hahahahaha!

--Bo

I have a friend here who uses the flats with this huge felt pick. It does sound like an upright. Yes Carol used to jam pillows under her bridge to mute LOL! D