Walter Murch invented the job he was hired for

Job titles are a record of what a field has decided is worth naming. For most of film history there were sound recordists, sound editors, and re-recording mixers — all of them understood as technicians executing someone else's intention.

The opening of this film is not an execution of anyone's intention. The helicopter that turns into a ceiling fan is an argument about how memory works, made entirely in sound, and it required someone to be treating the audio track as a place where meaning gets authored rather than reproduced.

Coppola's contribution here is real and includes the crucial one: he let it happen, and he approved a credit that did not previously exist. But the film is routinely described as a director's crisis and a director's triumph, and the thing most people can still reproduce from memory forty years later is a sound cut.