Riddonkulous

I am no chum, though I hang beside one. I am not glum, though I wear a somber hue. I ripen while the bees hum, While distant fingers strum, Feasts leave behind a crumb, And many succumb to my sweetness. I am no drum, though hollow at my core. Nor am I scum, though some would stain my name. A stone guards my heart all the same. What am I?