I dunno if you can get
that close on a fretted. Or, i guess it depends on how close you think "close enough" is. Especially because fretless sounds like fretless, but also, not all fretless sounds the same. String type and pickup and fingerboard wood and player all play into the sound. My fretless with maple fingerboard, Delano Xtenders each in series, wired parallel to each other, with La Bella White Gold Tapewounds does not sound anything like Jaco playing with rounds through the single coil bridge pickup of a Jazz bass with an epoxied fingerboard.
Those semantics aside, i get what you're going for. And since you're really focused on the tone in that one tune, you can probably get close enough to be happy with the approximation.
I don't know what bass you have, but i'd start with trying to approximate a Stingray tone with your bass, however you can do that, because that's what Pino used on that song. Then from there try to do the fretless approximation.
If you have an active bass, give a little bump in the high mids and run it through a chorus. Otherwise put an EQ before the chorus and bump the high mids. The chorus will come through nicely with those frequencies emphasized. Every chorus pedal has slightly different controls (Or the same controls with different names), but generally i'd say keep the speed relatively slow, and maybe a mid-level intensity or depth. A chorus is just a second channel with a very slight delay and sometimes slight pitch shift. You just want it coming off the clean note you're playing ever so slightly to replicate a finger hold a note without a fret to keep it exactly on frequency for the fretless approximation, plus there's also chorus added to the track. So you can find a chorus sound that approximates fretless, and then increase the dry/wet blend a bit, or make some of the parameters a little higher to add some extra chorus.
I might also boost the lows a touch and pull back on the highs, just from what i'm hearing in the song. But you gotta adjust according to what you're hearing from your bass and amp.
If you have a pedal or digital fx box that allows micro-tonal pitch shift with an lfo, that could come in handy replicating the free movement of a fretless. But be
very careful with this. Using either a random lfo shape, or a sine wave if it doesn't have random, set the lfo speed very slow (like 5Hz?), and have the lfo shift the note about 3 to 5 cents sharp & flat. Subtlety is key here. You might want it so subtle you don't notice it unless you're looking for it.
And then a really light reverb with the decay all the way down, or a light short delay, almost indistinguishable from the chorus might add just the final touch.
However, the cost of getting the different pedals to do this (EQ, Chorus, pitch shifter, reverb, delay), or the all-in-one digital fx box might be the same amount of money as an inexpensive fretless from Sire or Squier. And then you have a fretless to play.
I dont have the cash to buy (or the skills to play) a fretless bass !.
As someone who plays fretted and fretless, i wanna say: Don't think like this.
You can play fretless. They're insanely fun. And if you just put in a little bit of practice with your finger accuracy and ear intonation, it's really not a huge issue to play fretless. Just pay attention to your technique and listen, which you should be doing even on a fretted bass. Don't rule out playing fretless, especially if a fretless bass costs the same as the FX needed to fake a fretless.
