As this was a piece I had never heard before, something became evident when learning the music by ear - especially when playing my private recording of it alongside the original. There were slight but noticeable shifts in tempo.
So what? Well, I believe there is something inherently human about music, and as you remove elements of "human-ness" you diminish the emotional connection with the listener - and in turn the appeal.
I have written before about quantizing, a process often used in music to sharpen up the accuracy of timing. This can be especially useful in projects such as music notation where timing must be spot on to produce an accurate result. This tool certainly has a value.
However the process of quantizing takes away one of the human elements of music. As mentioned in my Auto-tune commentary, we are not robots and should not strive to sound that way! It is natural to move slightly ahead of or slightly behind the beat from time to time when performing. A perfect snapping into the strict timing of the beat simply sounds un-natural.
Take for example the song "Forever" by Ben Harper (below). The song generally sits around 83-85bpm, however in some sections this becomes more swift, in a way not likely to be noticed unless you are clicking a metronome of some kind along with the track. These subtle variations help give the song life and help strengthen the connection between performer and listener. The listener is washed along with the song.
Let your music have life.