The correct emphasis in the word "simultaneous": two regulatory option
Options pronunciation of "simultaneously" (with the accent on the second syllable) and "simultaneously" (in fourth) in the modern Russian language are considered equal. The same can be said about the released "simultaneity" and the adjective "simultaneous" – the stress they can put as the first "E" and the second.
Both of these accents equally conform to the norms of Russian literary language, and both are considered correct. Therefore, the word "simultaneously" emphasis can be put "to taste" by choosing the option that seems most harmonious.
However, you should pay attention to what to say these words through "e" ("simultaneously", "concurrent" and so on) is unacceptable, and some authors of dictionaries emphasize this option as incorrect.
"At the same time": the emphasis in the Ozhegov, Dahl and other
Norms of the Russian language change over time, and the rules of production of the stress in the word "simultaneously" in the last century has changed too. Thus, in the famous dictionary by Vladimir dal compiled in the mid-nineteenth century, the correct emphasis in the word "simultaneously" mentioned in the third word. In the "Dictionary of deficiencies of Russian speech" Dolapchieva, published in 1909, as a normative also mentioned this option.
Some of the authors of more modern dictionaries and reference books of the Russian language still prefer to accent "simultaneously" considering, however, the variant with the accent on the fourth syllable "simultaneously" is valid. However, this view can be considered obsolete.
Thus, already in 1960, the dictionary Ozhegova is fixed to double the rate of the stress in the word "simultaneous", and variants of pronunciation given as equal, without specifying their preference for either option.
The same view was held by many other compilers of dictionaries: double emphasis in the word "simultaneous" appeared in the "Pronouncing dictionary," published by the publishing house "Russian language" in 1983 Pronouncing dictionary, in the dictionary of the Russian Academy of Sciences (2003 edition), the dictionary edited by Lopatin and many other dictionaries and reference books.
In the pronouncing dictionary Reznichenko, included in the official list of dictionaries containing the norms of the Russian language as the state language, also listed the double version of the rules, so the proper stress in the word "simultaneously" as the third and fourth syllable, can be considered as legally approved.
Interesting fact about stress "at the same time"
The word "simultaneously" in two accents simultaneously. This pun can remember the validity of the stress on any of the "E", it allows you to record that word by combining both norms. But to say "simultaneously" with two accents at once will not work, you will have to choose.
That is why the word "simultaneously" became the name for one-man show of Yevgeny Grishkovets, which premiered in 1999. The desire and the inability to get "all at once, simultaneously" is a key, perhaps the emotions of the play. And the name of the play is written this way: "Both", with the accent on the third, and the fourth syllable. And the double standard of pronunciation, according to Evgeny Grishkovets, inspired him so much. This solo performance he later called "the show with two accents": there was quite a lot of variability.