“Here is “Margaret Garner” at its best: the sprawling calamity of slavery telescoped into an intimately scaled portrait of love underscored by Danielpour’s melting lyricism and placed within the spare set designed by Marjorie Bradley Kellogg. The burden of such a broad and bewildering historical canvas as slavery sometimes overwhelms Danielpour and Morrison, but these shortcomings are redeemed by ruminative expressions of a mother’s love and heartfelt song.”