Live albums are presented as documents of a performance and almost all of them have been worked on afterwards. The practice is old, widespread, and mostly uncontroversial within the industry.
Where it becomes questionable is a matter of degree, and the degrees are worth knowing.
What is routinely done
Ordinary and largely unobjectionable.
Mixing, since a live multitrack recording is raw and requires balancing exactly as a studio recording does.
Editing between nights, assembling an album from several performances, taking the best version of each song. This is standard and generally disclosed in the credits if anybody reads them.
Removing technical problems — a dropped microphone, a feedback squeal, an equipment failure.
Audience adjustment, raising or lowering crowd noise for balance, which affects perception considerably and is rarely mentioned.
Where it gets more substantial
Common and less discussed.
Repairing individual notes or lines, replacing a bad vocal phrase with the equivalent from another night or from a studio overdub.
Re-recording instrumental parts entirely, which happens more than audiences assume, particularly where a performance was strong and the playing was not.
Pitch correction applied to vocals, which is now routine in most recorded music and is applied to live releases as well.
And in some cases, substantially rebuilding a performance in a studio while retaining the crowd, which produces something that is a live album in presentation only.
Why it happens
Reasons that are not purely cynical.
A live performance is a one-off event under difficult conditions, and even excellent musicians have imperfect nights.
An album is played repeatedly, and a flaw that passes unnoticed once becomes intolerable on the fiftieth listen.
And audiences, whatever they say, generally prefer the polished version. Genuinely raw live recordings sell poorly and are frequently described as sounding amateur.
There is a real tension between documenting an event and producing something people want to listen to, and the industry has resolved it toward the latter.
How to tell
Some indicators, none conclusive.
Crowd noise that is consistent in level throughout, or that does not respond to what is happening on stage.
Vocals with no variation in room sound between songs, suggesting they were not recorded in the same space.
Performances that are technically identical to the studio version, since live playing varies.
Credits listing a studio, additional engineers, or recording dates after the performance dates.
And the absence of any audible mistakes at all across an entire concert, which is not how concerts go.
The bootleg comparison
Which is where the interesting listening frequently is.
Audience recordings and unofficial soundboard tapes are unprocessed, and they document what actually happened.
The sound quality is generally poor and the performances are genuinely live, with all the variation, error and spontaneity that implies.
Many artists tolerate or actively support the circulation of these, and some have released archival series drawn from soundboard tapes with minimal processing, which is the honest version of a live album.
For anybody interested in what a band actually sounded like on a given night, these are considerably more informative than the official release.
The reasonable position
Mixing and assembling from multiple nights is production, and it is fine.
Repairing errors is a judgement call that most listeners accept.
Replacing performances wholesale while presenting the result as a live document is misleading, and the fact that it is common does not make it otherwise.
The simple fix would be disclosure, which some artists do voluntarily and which costs nothing. A note saying an album was assembled from several nights with additional studio work would satisfy anybody who cares and would not trouble anybody who does not.
The film equivalent
Worth noting since concert films raise the same question with an additional layer.
Almost every concert film is assembled from several nights, with the audio treated as described and the picture cut across performances.
Which means a single continuous performance on screen is frequently constructed from three, and the visual continuity is managed through matching costumes, staging and camera positions.
This is standard, it is well known within the industry, and it is essentially never disclosed to the audience.
The genuine one-take releases
They exist and are worth seeking out for the contrast.
A small number of artists have released genuinely unedited performances, sometimes as a deliberate statement, sometimes as archival releases from decades ago.
They sound different — looser, more variable, with audible mistakes and real dynamics — and the experience is closer to being present than any polished release manages.
They also demonstrate how much the standard treatment removes, which is the most persuasive argument for taking the question seriously at all.
Why it matters at all
A fair challenge, since the music is the music.
The reason to care is that a live album makes an implicit claim about what a performer can do, and audiences use that claim when deciding whether to buy a ticket.
A recording assembled from twenty nights with studio repairs represents a capability that no single evening will match.
Which is not fraud and does set an expectation that the live experience cannot meet, and it is one reason people occasionally leave concerts disappointed by performers who are entirely competent.