There have been some questions about the revival/restoration of Lucinda Childs and Philip Glass' DANCE. To address those questions, here are some comments from Philip Glass Ensemble Music Director Michael Riesman:
The three sections of "Dance" that were restored and are now being performed are Dance I, Dance IV, and Dance III. These are the only sections for which film was made. In the original production, Dance II and Dance V were performed without film. In recent years, Childs has presented the work with film sections only, with Dance IV replacing Dance II as a middle movement, and renamed "Dance II".
The restoration involved both image and sound. The image was transferred to digital along with the audio from the film. Since this audio was of relatively poor quality, due both to its optical format and to film deterioration, I was approached by the people involved in the restoration to find out if it could be improved. I went back to the original source materials and, using time-adjustment tools to synchronize with the film audio, replaced the entire audio track.
The album "Dance" was mixed from the same source tapes as the film track for Dances I and III. However, on the album, Dances II and IV were re-recorded. The re-recording of Dance IV was done without reference to the original and thus could not be synchronized with the film because the tempos are too different.
On the original recording for Dance IV the organ was a Yamaha YC45D dual manual electric organ, which was also used on the album for Dance II. On the album, pipe organ samples were used for Dance IV. As far as I know, no chords were changed in album version, but the use of samples, which are less aggressive than the electronic original, would have softened the dissonances.