So, who's suffered from the mysterious 'wandering tone phenomena' ?

meltedbuzzbox

Apparently you can never here the same thing the same way twice. Your ear will always pick up different things.

Listening to music before you play can have a weird effect too. 

We are complicated beings with a lot going on with our ears and the big grey thing in between them 

57Deluxe

Bio~Rhythms

Chalky

Alas our heads are more like modelling amps than pure valve tone. There is a LOT of processing that goes on between the sound entering you ears and you consciously hearing the modelled results. Your blood pressure, tension in neck and face muscles, mood, etc all can affect what you hear in your head. Plus your brain will highlight things it thinks your mind should be aware of (hearing your baby's crying in the white noise from the shower) and remove other sounds - if it didn't remove sound it would be impossible for you to talk to someone in a busy pub!

hotpot

I've just got off the quest for tone bus, It's never ending, it never stops. I just say to myself, why did you buy the last piece of gear! because it sounded fantastic, It hasn't changed, It's as others have said, It's all in my head.

ToneControl

Sometimes, sitting the same chair, with the same acoustic guitar, it doesn't sound right.

So, I've assumed it's likely to be human variation from day to day