hi! sorry for the long wait
@sibilant is correct in their explanation!
In the traditional Māori culture, instruments were interstitially linked to absolutely everything, from day to day actions like hunting to the very core of their religion and creation mythos. Instruments were not just dead tools, but alive, living things, each instrument was an individual with it’s own name.
Pūtōrinoes are “both female and male” hence the two “voices” aka the two ways of blowing into it - just as sibilant explained.
For a more in-depth explanation I recommend the excellent Taonga Pūoro book by Brian Flintoff
A video in which Richard Nunns plays and explains about the Pūtōrino
Sorry for going so into depth about this here, but, in adding these instruments I read the entire book and every article I came across as I became more and more absorbed in how the traditional Māori instruments and music fitted into their lives, their religion, and how it was almost lost, but due to these people was luckily recovered.
Wanting to communicate this succinctly was also part of the reason for the wait.Thank you again sibilant for answering. :)