While visiting a high school choir class, the anthropologist in me found ways to introduce vocal art to illustrate some of the variety of music expression. Surely there are more or better references to sample, but these came first to mind:
-(Swiss; USA) yodeling
-(USA) work songs to synchronize group exertions
-(USA) Sacred Harp (shape note singing) in hollow square
-(USA) rapping (cf. Bobby McFerrin vocal percussion)
-(USA) vocal jazz 'scat singing'
-(Scotland) mouth music (imitating instruments)
-(ancient Britain) slaves brought to Imperial Rome: novelty of singing in 3rds
-(Bulgaria) women's chorus singing in 9ths and 7ths
-(Central Asia) Tuva "throat singing"
-song circles for healing
-(India) mantra repetitions
These could be extra-credit assignments for students to report to the class (or in writing to the teacher), for the teacher to playback samples (Wikipedia; Wikimedia), to demonstrate and challenge students to produce each of these.