On the 2014 release of the March 1974 concert, Freddie sings, ‘Soldier, sailor, tinker, tailor, ploughboy...’ The distortion of the word ‘ploughboy’ is likely the most glaring use of pitch correction on the 2014 version of the March concert, one that most of us here can agree on.
It’s very hard to say what the note was originally. If Freddie simply sang a flat note, it’s unlikely that he would have missed it by a great amount. In that case, the note wouldn’t sound so obviously unnatural, as it wouldn’t have needed to be adjusted all that much. It’s also perhaps possible that Freddie’s voice just cracked, leading it to sound as garbled as it does. The theory I lean towards is that Freddie sang it this way:
Matching the studio notes for ‘Soldier, sailor, tinker, tailor’.
For plough-boy, singing an A for plough, then an A for boy, descending down to an E.
Now, the studio version has the notes here as C for plough, A for boy, descending down to an E. This is what is recreated on the 2014 release.
Knocking ‘plough’ up three semitones would likely cause the level of distortion that we hear on the 2014 release. Thus, this supports the notion that Freddie did not flub the note. Rather, he chose not to attempt the high C at all, singing the more realistic A instead. What we hear is an attempt to make it sound like Freddie did indeed go for and hit the high C.
To reaffirm, this is only speculation – we simply can’t say for sure what the note originally sounded like, whether it's actually been pitch corrected, and if so what warranted its alteration.