Small-but-funny side-effect of meditation and other attentional training:
You start noticing these weird pseudohallucinations. Brains are funny and like to pattern-match. Currently, the dishwasher is sort of playing music at me, the gaps in the rhythm filling automatically.
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It can be a very good practice (and a quick way to attain a trance state) to pay some attention to these attentional artefacts when they show up.