Thanks Daniel - definitely helpful!
Most likely I would think the experience was either "the arising & passing away", a brief formless realm exp., or a state-shifts between between insight or Jhana. I was experiecing Jhana on this retreat at at the time of these events was in deep Samahdi (my mind very bright & aware).
I listen to one of your podcasts recently when you mentioned many different versions of "the arising & passing away".
My first arising and passing away was about 13 years ago on my first retreat. I was listening to outside when I noted: as the sound hit my ear as vibration, it was precieved as vibration and manifested on the body as vibration (sensation). At this point of self-observation the body dissolved completely & I could not distinguish betweeb what was body or what was outside. I felt like a ball of energy vibrating inside a universe of vibration. So I assumed that particular experience was "the arising & passing away". It seems from your podcast the experience has many forms.
I have just started reading MCTB too - thanks for the help, advice & great inspiration!