I cannot say whether the DVD is synched or not. It is common to go in and fix mistakes after the recording of a live show for release on DVD. However, I saw Celtic Woman live last night in Nashville and most of the show was synched. I am recording engineer and 14 year music industry veteran and can tell you that every up tempo tune (vocals and fiddle) was performed to pre-recorded tracks. Not only could you tell visually, the tracks had a different sonic character than the live vocals. The tracks were brighter and much more sibilant. Also, the real fiddle had a much more warm tonality with more string scratch than the tracks. Now, they did appear to sing the more exposed down tempo stuff and Mairead actually played at least one tune. It was pretty obvious when the whistle player strolled across the stage for a solo that there was no microphone in sight (although he appeared to play the rest of the show quite well). Also, during an encore I noticed Chloe dancing in rhythm before the music had started which indicates she had a track in her in-ear monitors. I am unsure about the harp stuff, but I have my doubts.

My question is this: Why do such obviously talented performers (they obviously recorded the backing tracks at some point) feel the need to rely upon tracks?