It may astonish some instrumentalists who may hum in an fit of absentmindedness but there are actually people on this planet who LIKE singing. I am a singer first and foremost, any other instruments that I play come far far back. I am not a singer because I am an egoist but because I like to use my voice and I love listening to other voices. Sing around nights sound like something I would love. Our local song circle sounds a bit similar however we don't discriminate against people who also come to play instrumentals, we're just not all good at jamming together on unknown songs with instruments. The first thing I do to learn a tune that someone plays on fiddle or banjo or whatever is start singing it. If I can play it with my voice I've got a good chance of playing it with my fingers.