Steamy Windows Bass Sound

I had a listen to this version:


Sounds like keyboard to me... though you could get that sound with a 5-string and envelope filter or Auto-Wah with a tad dirt.

 

Thanks for the link! And I agree: almost certainly keyboard.

To the OP: as noted, you can try to replicate that tone with envelope filter (auto wah), perhaps something like the Bassballs which also adds dirt. Adding an octaver can increase phatness. Also, you could look into pedals that give the synth bass sound: these typically have octaver, dirt, and envelope filter built-in. I don't have a recommendation but you could try searching for synth bass pedal threads here in the FX forum.