How do they fix performance glitches when doing post-production on "live" recordings?
November 16, 2009 10:18 AM   Subscribe

How do they fix performance glitches when doing post-production on "live" recordings?

Assuming that they don't have multiple performances to splice together, how do they correct a singer's pitch or fix an instrumentalist's late entrance?

If they simply record a new part in the studio, how do they approximate the venue's acoustics?
posted by Joe Beese to Media & Arts (8 answers total)
I always thought this was part of what makes live performances awesome - the glitches, adlibs, etc.
posted by radioamy at 10:28 AM on November 16, 2009 [1 favorite]

Multiple performances are recorded (sometimes even the rehearsal is recorded just in case), and efforts are made to find a better piece of audio to splice in.

You'd be surprised how many times you can fix something like this with a similar section from another place in the tune, or from the run-through earlier that day, or from the performance in the same venue the night before.

Pitch correction can't be done after the fact (unless there are multi-tracks, which there often are).
posted by Aquaman at 10:28 AM on November 16, 2009 [1 favorite]

They will almost always have multiple performances to splice together, and you can also splice from the same performance.

That aside, live recordings are typically recorded to multi-track tape, just like a studio recording. Each instrument or singer gets its own track. (Drums may get multiple mics and thus multiple tracks.) There are extra mics in the crowd to capture audience noise and how the band sounds from the audience. Unidirectional mics are used so that each element is as isolated as possible. There will be leakage, but each track will be predominantly the desired sound, and this is generally good enough in most cases. This recording is later mixed down to stereo (or surround) in the studio.

Pitch-correction may be done live these days -- that is, the singer's voice that goes out into the venue is already pitch-corrected, assuming they know in advance that they'll need it, so that won't necessarily need to be done in post.

As for approximating the acoustics, they probably don't go to this length, but it is possible to "sample" the acoustics of a space and reproduce it nearly exactly later. This is called convolution reverb. More likely they simply dial in the approximate size of the venue into their effects unit or software, and tweak until it is close enough to blend in.

This is a lot easier than it used to be, obviously, but it has long been possible to get good results. Peter Gabriel's 1983 live album Plays Live admits in the liner notes that some parts were re-recorded later in the studio and even calls it "cheating." It is almost impossible for the casual listener to tell where this happened.
posted by kindall at 10:38 AM on November 16, 2009 [4 favorites]

They nearly always have multiple performances to draw from. Data point: The album and the film of Stop Making Sense is actually three separate nights spliced together.
posted by Cool Papa Bell at 10:51 AM on November 16, 2009

A famous example of a ridiculously overdubbed live album is Live and Dangerous by Thin Lizzy. Reading up on the making of that might give some insight, there is plenty of disagreement over it.
posted by fire&wings at 11:05 AM on November 16, 2009

Peter Gabriel is renowned for 'improving' live recordings (albums and DVDs) with overdubs / re-recordings. This talks about him renting a hangar to get 'authentic' acoustics for this process...
posted by valleys at 12:02 PM on November 16, 2009

Kiss Alive II has lots of post-production polish. And there are quite a few albums called "live at the _______" which were, in fact, recorded at that venue early on in the day (with multiple takes as needed) and then had the audience noise and stage patter from the real show tacked in later for the released recording. There are a few 'live' albums that were actually just recorded 'live in the studio' with a few friends of the band invited around. And I own one live CD that is, in fact, recordings of the band rehearsing for their upcoming minitour in a rehearsal studio with audience noise and stage patter added in later.

But as said above, cheap and easy multitrack recording makes corrections cheap and easy afterwards.
posted by K.P. at 2:18 PM on November 16, 2009

Often they tape a dry run earlier in the day and use that as B-roll to cut to if there's a glitch in the live version.
posted by twistofrhyme at 9:19 PM on November 16, 2009

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