Pitching is something that comes with practice , though you SHOULD be able to hear the guitar or fiddle ! The 'Ear'ole'trick is to pull the ear slightly forward with the fingertips , so that the sound is transmitted along the hand and straight to the ear .
There is NO doubt but that the prevalance of PA is not doing some of our less experienced singers any favours ! It's a LOT easier to develop voice projection if you do it without PA .