You don't have to ask around too much to hear a story like this:

(Alan, at a friend's wedding in Glasgow, 2005) "The 'band' consisted of 2 guys toting guitars and using backing discs - the backing was really cheesy, quite obviously cheap karaoke stuff. They were just about OK to begin with — the singer carried off some stuff well enough, but his style never altered, and they hardly communicated, so they soon started to lose the audience.
The vocals seemed to tire and crack up as time wore on, so they turned up the backing volume to compensate and then started repeating songs they'd done earlier. Eventually the whole thing got just unbearable - we actually felt trapped in the room with it! They took nearly an hour's break which, when you consider it, was a bit of a cheek, but actually it was a relief; what little atmosphere there might have been, though, had just fallen completely flat.
We sneaked out the hotel like guilty schoolkids just before 11 when the newlyweds went upstairs to get changed. We met quite a few other couples leaving and saying much the same:
'... we feel terrible sloping off early, but we just couldn't stand another minute of that racket!' We heard later that there were only a few people left at the end ... it was a real shame for the bride and groom - who were mortified -  because the rest of the day had gone really well."

This is honestly not scaremongering - it can and does happen. You have to remember that you - and your guests - will have your music as a backdrop all night ...

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