Hohner 572BXC Hot Metal Harp. Key of C The 10 hole diatonic Hohner 572 Hot Metal Harmonica has a smooth and comfortable plastic comb brass reeds and stainless steel covers. Its an economical harmonica for those looking to rock out while playing rock n roll or lay down some blues. The 572 Hot Metal is similar to Hohners Old Standby harmonica but with a little more edge and a brighter sound. Its tough durable easy on the wallet and a great starter harp for those just finding their chops.