Thanks for this great post fivestringgecko!!!
I think you are right. I have listened to all clips again and now i also think it is wah. Somehow I had in my mind or read somewhere that he used an envelope filter in those days or a phaser. I couldn't quit grasp exactly if it was an envelope filter or a phaser or both together. But it sounds more like a wah I agree.
I have tried to emulate those sounds on the Spectrum and came up with some nice sounds but none were exactly right. I also have a Dunlop bass wah and will hook it up again with my fretless bass and see if it comes closer.
What strikes me the most on his sound is the really nasal sound with not much sustain like at 2:03-3:14 or so of "Flight...". it is not just his fretless but there is some effect on it. If you compare it to the sound of the beginning it sounds very different. Maybe he uses his way cocked, so fixed in an in between position? Or something else? Or maybe he has an out of phase switch on his bass or something? He is using this sound fairly often in other songs as well.
No sweat. I'm a bit embarrassed to admit it, but I haven't really listened to much of Alphonso's work, and I really enjoyed diving in to analyze. I always paid much more attention to Weather Report with Jaco. Your link to Flight to Hamstead was the first time I've heard any of his solo work, and I'm already checking out the rest of that album!
I think the comparison you're talking about for Flight might be as simple as having both pickups on at the beginning, and dialing to the bridge at 2:03, which would definitely create that more nasally tone.
I've already started down the rabbit hole... A little googling comes up with a couple key photos, Him with a wah, and some interesting controls on his bass with dual P pickups.
5sg.