@Nudhul absolutely true, hence my attempt at differentiation via the word "perceived",
if i am thinking consciously about "mmm banana" then suddenly hearing, overlayed my normal conscious inner speech, my imaginary boss shouting at me that i need to do the job, completely out of context for my brain. that overlayed thought is potentially percievable as "thats not what i wanted to think!". Now, what if this intrusive thought becomes louder and stronger than my controller inner speech? The extremest version of intrusive thoughts, might even be perceived as true audio even, and not even a thought anymore. Boom, auditory hallucinations.
some thought in the brain that i could have, could be connected via a long neuron loop-de-loop, to a beginning of some auditory memory, that could be forced to play. like a markov's bot. But rather than having to choose a direction for itself, a brain can run several paths at the same time. so i'm doing my normal thought pattern of "hungry, bread, butter, ham, toasty, yummy", but the concept of butter would fork into two very strong connections, one being "yummy", the other being a dormant connection to a part of my unconsciousness or another thought train, which would circle back somewhere else and hit my waking consciousness processing part of the brain with the signal for the memory of mozart's lacrimosa, causing that to be stuck playing in my head with no discernible cause.
maybe i ate really tasty salty buttered toast a year ago while listening to lacrimosa, and that created that dormant connection. now these connections can be so much stronger, if accompanied by amazingly strong forked connections. And those signals from those multiple forked connections that you lose control over because of their overwhelming strength, can start to override whatever strong signal path the conscious part is trying pay attention to most. it becomes a competition, "what is the correct signal, they are all so strong!!!"
i am NOT a medical professional these are my hot opinions