Brutish Musician

When Brutish Musician enters the battlefield,
choose High or Low. At the beginning of each
end step, choose the option not last chosen.
Whenever High was last chosen, other creatures
you control get +2/+0 and have menace.
Whenever Low was last chosen, creatures your
opponents control get -0/-1 and lose vigilance
and first strike and can't gain those abilities.
(Until High is chosen.)