Links

www.harmonicwhirlies.com 
(musical instruments created and manufactured by Sarah Hopkins)

www.australianmusiccentre.com.au/artists/hopkins-sarah

https://mortonmusic.com/archives/composer/hopkins 
(Sarah's choral music publishers)

www.annenorman.com 
(Anne Norman, shakuhachi player and composer)

www.margaretbrandman.com 
(Margaret Brandman, composer and music educator)

www.tranquanghai.com 
(harmonic overtone singing)