Hmm... two things going on here -
that weird rubbed fretless sound made famous by Pino Palladino on those Paul Young albums and
slap bass, where you play with your thumb, as made famous (started by?) Sly & The Family Stone with 'Thank You Falettinme' or however it's spelt, and all over our dear friends the Chili [sic] Peppers. And yes, Level 42.
What was up with that guy Eberhard Weber, who did some vaguely new agey stuff for ECM in the 80s? I guess that was fretless. I think he plays on Kate Bush's 'Mother Stands for Comfort', if anyone who knows that can hear what I'm thinking of in their mind's ear..
Incidentally, Pino Palladino re-invented himself in session with ?uestlove et al on D'Angelo's 'Voodoo', and however much that gets dissed for being rockist and pandering to some bullshit realness, I fucking love the rhythm section on that album.