The fonts are mostly built by Monotype, with the exception of CJK fonts which are built by Adobe, in the regular way of designing and building fonts.
Re:Google Noto Fonts
by AlexCoventry on Saturday October 08, 2016 @08:25AM
(#12666722)
Interesting. Is that clear from the fonts themselves, or did you learn it out of band?
https://arxiv.org/pdf/1508.06576.pdf (See p. 5 for examples.)