He was one of the early members of the International Phonetic Association, founded by Paul Passy in 1886, alongside leading British phonetician Henry Sweet, and served as its president from 1888 until his death.

[1] In 1981, German phonetician Klaus J. Kohler described Viëtor as "the most outstanding figure in the field of descriptive and practical phonetics of individual languages in Germany at the turn of the century".

under the pseudonym Quousque Tandem (taken from the opening words of Cicero's speech to Catiline), which spurred the Reform Movement in foreign language teaching in Europe.

[4] He also revised and edited works by the British phonetician Laura Soames, including Introduction to English, French and German Phonetics (1899).

Viëtor also compiled Deutsches Aussprachewörterbuch (1912), which likely played a role in inspiring Daniel Jones to publish the English Pronouncing Dictionary (1917).