A midlength balanced rotor comprises a rotor assembly for rotation about an axis of rotation defining at least one of an axially extended, radially concentric, centerline borehole; an array of radially or tangentially distributed, axially extended pockets; and a series of radially or tangentially distributed, axially extended slots. At least one balance weight is positioned within at least one of the axially extended, radially concentric, centerline borehole, the array of radially or tangentially distributed, axially extended pockets, or the radially or tangentially distributed, axially extended slots to balance the rotor assembly. Alternatively, at least one balance correcting mass is removed from at least one of the axially extended, radially concentric, centerline borehole, the array of radially or tangentially distributed, axially extended pockets, or the radially or tangentially distributed, axially extended slots to balance the rotor assembly. In addition, a method of midlength balancing a rotor comprises the steps of providing a rotor assembly with at least one of an axially extended, radially concentric, centerline borehole; an array of radially or tangentially distributed, axially extended pockets; and a series of radially or tangentially distributed, axially extended slots; rotating the rotor shaft about an axis of rotation; determining unbalance of the rotor shaft; and adding or removing weight to at least one of said an axially extended, radially concentric, centerline borehole; array of radially or tangentially distributed, axially extended pockets; or series of radially or tangentially distributed, axially extended slots, to balance the rotor shaft.