I'm really enjoying this! The opening piano solo sounds like a warped variation of Debussy's
Gollywog's Cake Walk.
It reminded me of the tasteful use of wah by some of the Canterbury bassists:
The solo in Fol De Rol is very mellow, yet there is a wah being gently rocked throughout it. Some of those Canterbury bands also featured organ with wah, so for them it really was just a texture or filter effect rather than a raucous rhythmic device.
Kevin Ayers used one on the Soft Machine track Joy of a Toy:
Maybe the wah was the titular toy here? Presumably Kevin is using his Rivoli bass.
And speaking of Rivoli bass with wah: