Record a piano thats not playing through PA

Hard to phrase the question. At church we use audacity to record the sermons and it’s great but when we record the singing the piano is very low. If we mic up the piano it will be too loud. How do we do this?

a device called a mixer is used to adjust the relative levels from different microphones, e.g.
http://www.maplin.co.uk/3-channel-microphone-mixer-36158