Lewis-Williams theorized that paleolithic cave painters used drums and breathing techniques to enter ASOCs while making the paintings. I think that theory has taken some hits in recent years but it was always a neat mental image.
A pretty specious one IIRC; he compared San rock art to paleolithic European cave art and -- despite the fact that the San do not practice shamanism -- concluded both types of paintings are records of shamanic trances. Like I said, the theory has taken a few beatings in the past couple of decades.