The process emerged from the problem of on set/location sound recording quality due to the cumbersome technology of earlier years. But today the problem is noise pollution. It is hard to record good sound on location today - too much extraneous noise.
Of course some directors use location sound, using methods developed for documentaries. But sound is such an important part of movies that its reconstruction - dialogue, FX, Foley etc etc is considered to be a creative process, not a budget process.
Editing of picture, as well as dialogue performance, is another reason for (re)dubbing. When you cut pictures together you create a spatial relationship between the shots. The associated sound has to fit into the space. It is a lot easier to do this afterwards in dubbing - you start with a 'spaceless' voice recording and then add the echo, EQ and ambience that place the voice in the picture space.
Leone, and many other Italian directors, recorded the most primitive of guide tracks on set, knowing that they would recreate the sound in the controlled environment of the studio. Leone took it one step further in often choosing non-actors for the look of their face, and getting in a professional later to 'do' their voice. He also took a lot of liberties in changing the original dialogue. And that led to strange dubbing artefacts - noticeable in Once upon a time in the West. You can't be me, I'm taken
The 'as released' cut done for US release is a hack job and the film is incoherent.
See if you can get the "Special Collector's Edition" (ISBN 0 7921 7272 8) having the virtue of being what Leone wanted.
(Of course, YMMV as to the value of "being what Leone wanted. :)
But anyway - it's just a movie...
<ducks and runs> You can't be me, I'm taken
My roomates and I had the soundtrack, and would randomly put our speakers in the window facing the street and blare the theme song. Could be heard blocks away. Was a lot of fun. "Pretending that you already know the answer when you don't is not actually very helpful." ~Migeru.
Many stylistic elements are present in both, Morricone was again writing the score, but it is different. More epic, more long scenes, more lead characters (4-5), and a not really happy ending. And more daring: the 12-minute opening scene (credits) is in essence just showing three ugly men being bored, and angel-faced Henry Fonda is the bad guy.
Our tastes have differed before, and the film may have aged, so I can't guarantee you'll like it, but even if not, perhaps it'll be worth it for recognising what inspired later filmmakers.
My roomates and I had the soundtrack
You mean that of The Good, The Bad & The Ugly, or Once Upon A Time in The West? *Lunatic*, n. One whose delusions are out of fashion.
"Pretending that you already know the answer when you don't is not actually very helpful." ~Migeru.
Bit o' Trivia: apparently original intent was to cast Eastwood, Wallach, and van Cleef as the 3 bad guys at the opening of Once Upon a Time. Wouldn't THAT have been fun!
:-)