Serious point - Its worth telling a trusted mate these choices and also make him/her promise to make sure that the church doesnt use a shitty stereo that plays the song at a low volume.
Of the funerals I have attended the past few years only one has played the music of choice to an acceptable volume. The last one I went to was a female friend of mine. Even though the church was huge it was standing room only because she was so well loved. Everything was beautiful and moving. Then as the coffin was taken from the church and everyone stood.....a pathetic, tinny version of her favourite song was played barely-audibly from the back from a cheap portable stereo.