If you'd like to observe St. Patrick's Day in a manner that doesn't require the guzzling of watery domestics colored green or endless jokes about getting lucky, here's an acceptable alternative: As Pratie Heads, Jane Peppler and Bob Vasile have been enthusiastically arranging and inventively interpreting Celtic tunes for three decades. Their 30th-anniversary concert guarantees a celebration of commitment, not of calendar coincidence. —Grayson Currin