I think it's largely a matter of your purpose for shooting the video. If you just need a record of the event for the sake of posterity or for something like grading the performance - you can get by with a static shot.
However, if the purpose is for some form of enjoyment -- I highly recommend trying to capture the moment by occasionally zooming in on the performer...gets some close ups on the face, the fingers working the instrument, do some upward pans where you start on the instrument and pan up toward the face, get a shot of two of them tapping their foot, etc., etc.
Get on youtube and watch some professionally shot videos of a similar type performance - you'll get some ideas from that.
I can virtually guarantee if the intent is to record something that the family might want to watch for enjoyment in the future - they will all be sleeping before five minutes has passed if it's a static shot.