I remember Bad Seed talking about this a couple years back and after looking through the performance, I think I found some possible overdubs:
At around 1:02 in the video, Freddie says "Shoot out" (which he normally does on the song), but listen to his tone. It sounds nothing like his vocals during the first verse and chorus (the vocal sounds MUCH more polished and louder in the mix).
Then at 1:10, Freddie starts singing "how do you think." At around 1:12, he gets to the line "without you." At that point TWO Freddie's start singing (one vocal track--the legit one, and the Rock Montreal vocal). It sounds like Freddie re-sang parts of the line in the studio using the same live phrasing. You hear these two vocals sing simultaneously during the entire second verse. This also happens during the last line on the second chorus (Hey--gonna get you too, another one bites the dust).
During the beginning of the improv, Freddie's tone changes back to normal (not sounding super polished). The entire improv is legit (meaning he sang it live--not touched it up in the studio).
When Freddie ends the improv (starting with "Another One Bites The Dust"), his tone goes back to the "polished" sound (with the vocal doubling happening again).
During the third verse (starting around 3:18), you can really hear the original live vocal underneath the re-sung/overdubbed version.
My conclusion is that most of the verses and chorus lines on the official version have been overdubbed and the improv vocals are 100% legit (non overdubbed).
From the first line I think you can tell there's two Freddie's on the track. It's not an echo (although it's probably intending to be one) but the two voices sing each line slightly differently to the other.
Ugh, that's the horrible audio mix on the 2001 DVD.
The picture however isn't bad, at least the band members don't appear to be suffering from Hepatitis!
Haha, really? I was hoping the user who uploaded that found some ways to mute other tracks or at least bring one out. I have wanted to get some tracks with just Freddie's voice live, or everything minus his voice live as well as other setups. Darn.