Penny whistle Key of C pennywhistle at DC Music. Thank you for your interest in the Penny whistle Key of C pennywhistle. Penny whistle Key of C pennywhistle Oak Classic Pennywhistles. One of the premier pennywhisltes in the world - created from premium triple nickel plated solid brass tubing and polished to a lustrous shine. Eash pennywhistle is capped with the unique Oak adjustable tunable mouthpiece. Available in key of C and D. Picture displays a pennywhistle in each key.