Bay seniors would be hard pressed to find a more relaxed concert setting than the one overlooking (literally steps from the sand) Miramar Beach at Half Moon Bay. Since 1964 the Bach Dancing and Dynamite Society has been hosting jazz, classical and world music performances in the intimate and recently renovated Douglas Beach House here just 35 minutes south of San Francisco. Coming up on September 13 is Kyle Eastwood (son of Clint) and on September 20 the Mary Stallings Quartet, both at 4:30. Wine and beer and light fare is served and weather permitting you can picnic on the deck. $35 and $45.