Abstract: A Boehm system clarinet having improved A key features. An auxiliary shaft having an auxiliary actuating spatula in rough proximity to the spatula of the B flat key affords operation of the A key with the right index finger without impairing the operation of that key in the normal manner by the left index finger. A temperature compensation mechanism on the auxiliary shaft assures that the auxiliary shaft cannot freeze up in response to temperature changes and impair operation of the A key in the normal Boehm system mode. An adjustable link mechanism disposed between the A and A flat keys makes the operation of those keys smoother and quieter.