there is a state of mind where the imagination and external world blend
it i sin heavy alpha waves
when i went to a zen temple once, during walking meditation, these nuns hit the STOP stick, when they hit it we freeze movement
they said "when your mind is pure you will still be hearing it "
tibetan singing bowls were birthed from the imagination for this purpose,
when you hit a singing bowl, lovingly that is , it echoes into silence
yet in that silence, the echoe continues in the mind, when you CLICK with the entrainment
and when you can imagine sounds yet HEAR them with your ears, this is a very profound alpha state, it might be hypnagogic, and it is psychedelic
a tibetan singing bowl can be had from ebay, a nice one , 4 - 5 inches diameter, for under $40
just some thoughts,