What is the singing technique of "blow harmony"?

"We Go Together"" (1956), and " "Ten Commandments of Love"" (1958), the Moonglows perfected the distinctive rhythm-and-blues vocal technique called " blow harmony," through which each singer's blown breath becomes part of a deeply resonant harmonic sound.

http://www.britannica.com/EBchecked/topic/724760/blow-harmony

Just found the following description:

"In the early 1950s, groups like the Ravens and Five Keys pushed vocal blending techniques from the r & b realm to doo-wop with the use of "blow harmonies." This practice, wherein sounds like "ha-oo" resulted by abruptly forcing air out of the mouth, replaced humming as the predominant form of background support."
http://www.shsu.edu/lis_fwh/book/roots_of_rock/Doo-Wop2.htm