The Legendary First Recording
In 1978, Bob Woods and Jack Renner took the first of many risks that are characteristic of Telarc’s history. On the cutting edge of recorded sound technology, they made the first commercial classical recordings in the U.S. in the digital format. One of those recordings was the now legendary Tchaikovsky 1812 Overture, performed by Erich Kunzel and the Cincinnati Pops Orchestra. The recording featured the first-ever digitally recorded live sound effects—digital cannons.

When the 1812 was released, the cover read "Caution! Digital Cannons," and the interior of the booklet warned the listener that "the cannons of the Telarc 1812 Overture are recorded at a very high level. Lower levels are recommended for initial playback until a safe level can be determined for your equipment." Reviewers also issued cautions: "Just be sure the volume isn’t so loud that one of the shots spreads pieces of speaker cone all over your floor," (Digital Audio); and "Its peaks would crack your window panes and maybe your speaker cones, too." (Knight-Ridder Newspapers). The disc became Telarc’s best-selling recording of all time, with over 800,000 copies sold, and for well over a decade has been the audio demo disc of choice.
_https://elusivedisc.com/erich-kunzel-tchaikovsky-1812-overture-ultra-hd-cd/

Я так понимаю , что ЖИВЫЕ пушки записали отдельно в поле . Потом смикшировали увертюру и пушки , формат записи ( цифровой ) позволял .