One of the finest pieces of Australian orchestral music written in the 20th Century, in my humble opinion. Written in 1968, this predates the iconic ocarina choir in Ligeti violin concerto by a good 20-ish years. If you know of other massed non-traditional instruments used orchestrally, please let me know!
I'm embedding the 5th movement here, but strongly recommend listening to the whole five-movement cycle.
It reminds me of home.