There's been a fair amount of discussion recently about (classical) artists miming to recordings in performance. The LSO have been told that, at the Olympic opening ceremony, they will be miming to music that they have already recorded. Tenor Jonas Kaufmann recently admitted to miming to a pre-recorded performance of the Champions League anthem at that tournament's final in Munich. And we all remember the chamber performance at US President Obama's inauguration in which the musicians didn't play live for fear of their instruments snapping in the cold.
there was no miming for the students of the Royal College Of Music on a weather-beaten barge during the Jubilee Pageant flotilla, when perhaps there should have been, for the sake of the artists.
It's a treacherous area. I myself was involved in preparation for a performance last weekend in which dancers from a local college were to perform to our live performance of a Bach motet. A final rehearsal was unsuccessful: the dancers had prepared their work to a pre-recorded track and dealing with the inevitable fluctuations of a live performance was seen as too great a risk. We were dismissed. It was a pity that we were unable to take part in the performance. There were also more serious concerns, as others in the choir turned to think of the reaction of the audience who might have come expecting a live performance - and the knock-on effect to the reputation of the group.
In the end, the performance I was to be involved in excluded the live musicians for expedience's sake. The principal draw of the concert was the dancing troupe, not the choir. Colleagues with more experience in performing for choreographers tell me that working to live performance is a notoriously tricky area. Performing to a track is not only simpler (fewer people in the space, less technology/mics/mixing) but also more dependable in terms of fluctuations of tempo, of timing.
This is one of the reasons why the LSO will mime to their music at the Olympics, to give more security to the temporal organisation of the event. This is not to say that the LSO, or any top level orchestra are incapable of playing to a given pulse, even without a click track. I can imagine that one of the reasons the organisers got cold feet is that - as in my experience with dancers - they are preparing to music recorded with a different conductor to that whom they will have at the ceremony. Yet, like a top orchestra, a top conductor is capable to reproducing a pulse simply from a marking.
Moreover, the technology exists for extremely accurate reproduction of timings in music. In the past I have been involved in live performances of film scores designed to synchronise exactly with the film. Performances of Howard Shore's score for the Lord of The Rings alongside the film (here's the inevitable cameraphone video) were achieved with a video counterpart to the score for the conductor. This is necessary as the fluctuations of tempo are almost insanely complicated: not only does the written music change meter [sic] with great frequency but the pulse of the music changes within that meter. Such is the mature of live music making, which, once recorded with the film, comes to be regarded as fixed.
Despite this the trend continues for the event organiser to try to find ways to control the music underscoring spectacle. Naturally, hiring a group of musicians is more than simply adding the frisson of live performance. There are other issues of finding time to balance or sound check, hosting the artists (and their instrument) and catering. One hardly need mention the cost. However neutralising or replacing live musicians not only ignores but actually questions the ability of those professionals who have been contracted to perform. This is all part of a nebulously interconnected trend to do with amplification and balancing, auto-tuning and a general ignorance of musicianship (not to mention the character of individual and ensemble music-making) which is a worrisome cloud on the horizon of professional music making.