When we chose a piper for our wedding we were lucky to find someone whom had a youtube channel of his playing. This made it possible when we were choosing songs to not only hear the song, but to actually hear how he sounded playing it. Another thing you can try is to ask the piper if he can also play the penny whistle, for portions of the ceremony where we wanted to still have music but not such a powerful sound our piper did this and it was a great addition.