Ceramics are problematic due to huge tolerances vs other types, as well as value drift vs temperature, and yes, microphonics as they said (but personally I think this is overblown in a guitar application.... diff story in a high gain amp). This refers to old style disc types; newer multilayer ceramic capacitors or MLCCs (ones with the NP0/C0G dialectric as they say in the vid, but fail to point out applies to ceramic caps especially) do not have these issues and are the ideal thing to use for super small cap values, e.g. in the pF range due to being cheaper than other types that go that small (except ceramic disc, which are cheaper still but suck). For higher values (nf to lower end of uF) polyester (film) are cheaper. Due to this reason, I wouldn't use any type of ceramic cap in a guitar tone circuit - film caps are the most cost effective and quality type you can get for that value range. Maybe in treble bleed circuits tho.