original

restored,
normalized level

restored, equivalent
perceptive level

The Cure, "Cold", live @ Printemps de Bourges, April 10th 1982

How ?
L&R channel alignment : level, phase, and spectrum, the last by means of spectral matching.
This is useful to correlate the music image, decorrelate the audience image.
Denoising, master EQ and master limiting.

original

restored,
normalized level

restored, equivalent
perceptive level

The Cure, "A Forest", live @ Hammersmith Palais, December 3rd 1981

Same technique...
...but with a less desperately bad original recording.

original

restored,
normalized level

restored, equivalent
perceptive level

The Cure, "The Figurehead ", live @ Amsterdam Carre Theatre, May 6th 1982

How ?
Signal is split in 5 bands, each band processed independantly
For each band : denoising, limiting, L/R balance
This one is useful to get a heavy, compressed sound out of a bootleg (when possible)

(listen to this one
on headphones)

original

corrected stereo

The Cure, "Other Voices ", live @ Whiskey A-Go-Go, LA, July 7th 1981

This a stereo correction only.
In bootlegs, there are not only ∆I stereo problems, but also ∆T problems.
This one is an example of a combined ∆I-∆T correction, goal is to have Sn & Lead in the middle.

original,
soundboard recording

(this one is also better on
headphones)

'matrixed'
(mono compatible)

original,
live recording

'matrixed', with added stereo
(non mono compatible)

The Cure, "Siamese Twins", live @ Ancienne, Bruxelles, June 11th1982

Example with two disctinct sources mixed together - bootleggers call the result a "matrix".
Typically, it's a soundboard recording mixed with an audience one (SBD + AUD).
The extra problem here is time synchronization between both versions.
The 'matrixed' version is less clean, but warmer than the sterile SBD version.