STERLING HEIGHTS -- Susan Tedeschi and Derek Trucks have created a sturdy model with their annual summer Wheels of Soul Tour, whose many musical merits were demonstrated yet again on Saturday, July 21, at the Michigan Lottery Amphitheatre at Freedom Hill.The show was once again all about excellence, with the Tedeschi Trucks Band, Drive-By Truckers and the Marcus King Band joining forces and for a night that cut showcased diverse but kindred approaches -- from the former's ambitious improvisational bent to the latter's bluesy roadhouse burn -- all with distinct Southern flavors.