The ancients believed that the frequencies they got by blowing into it put them into a "dream state", a relaxing higher state such as the theta state.

I think that modern research on sound frequency and what it does to our body can safely cross out the phrase "believed" from his sentence ;)

Nevertheless, I have some doubts whether it is possible to create an instrument with a similar sound and effects thanks to a PVC pipe ;)

Nevertheless, great fun :D