Music is SUCH a major part of my act - it is what links my work together as well as bring the audience in more. Music can play a HUGE part in a show and take it to an entire new level. Next time you are watching a TV show or film turn the sound down - then listen again with the sound. You'll see how important the music is to set the mood and tone of a show. It's exactly the same with a live performance. Whether you do close-up, kids parties, mentalism or stage, having music can really enhance an act.
As I said, it can be used to heighten emotions from pathos to humor. It can also help in character development. As Charlie Chaplin music is VITAL and it enables me to take people on a journey in my show. It also helps me stay in character much more easily.
The one advice I give, when asked, is if you are looking at adding a piece of music in to your act, play it to friends to get their opinion of the piece. For example, if you are doing something dangerous using fire, choose a piece that reflects the emotion and drama you are looking for. Play it to several people and ask them what images the music conjures up. If they say dancing swans then perhaps it's not the right choice of music.
David Copperfield is a great example of the right music for the right piece of magic. He often uses lesser known songs from famous artists and/or music from film scores.
Recently a friend played me a piece of music with a promotional video he wanted to use. I told him it sounded like I was at a funeral!! I played him something else and it completely changed the entire feel of the promotional video. Music is very powerful and I think too many magicians underestimate the power it has in performances.
Also, far too many magicians use standard 'magic' music that others are using. This just shows no imagination or care. If you are going to spend time and money on an illusion or a piece then spend time on finding the right piece of music.