If you are wanting live music
for either the service or the reception it certainly pays to shop around.
At a wedding I recently attended the bride had set her heart on a string
quartet to play at the church and found an excellent one at the local
University music department who charged only £140 for 2 hours.
Bands and singers may charge less for mid-week events than they would for a
Saturday night.
If you are wanting a disco at a formal venue, they may insist you use their
choice of DJ who has his equipment permanently set up there but for smaller
private venues you could get a friend with a good sound system to do it for you.
Remember to provide a good mix of music - the over 50s will expect the Rolling
Stones! It is a good idea to borrow a few CDs (all carefully labelled so
they can be returned) or buy a few cheap compilation CDs such as Best of the 60s
or whatever.
Remember to check that the venue has a licence for music if you are doing
your own.