A topic that often comes up is what did the Beatles do that were truly firsts. Often they're credited with things that they weren't first with but, as they were the biggest band, they got more attention for than others. For instance they weren't the first to do a concept album despite Sgt Peppers being often cited as such. They also weren't the first to leave singles off albums.
I thought it would be interesting if our collective wisdom could be brought to bear to come up with something like a definitive list. No trivial thing will be too small
Some I think will also be applicable only to the pop/rock genre. Things they did might have been done in classical or jazz realms, but that doesn't mean using them first in a pop/rock context isn't of some significance.
Anyway, here's a few to kick off. Bear in mind part of the point of this is to be corrected if a proposed first is incorrect. Sometimes the counter example will be even more interesting.
First backwards instruments to be used on a rock recording (Revolver)
First intentional use of feedback on a rock recording ( I feel fine)
First stadium concert (Shea)
First printing of lyrics on a record cover (Sgt Peppers)
Now here's one I'm not sure is a first but I was wondering. Was A Hard Day's Night the first No1 album to be entirely self-penned by the performer? I know this is a tricky one as the US version was a soundtrack rather than the UK studio album. But it would have been No 1 in the Us if released in the UK form so I'm happy to fudge this.