A set of 4 Hohner blues harps and Marine Bands, with keys F, A, C, and D. - Model: Marine Band & Blues Harp - Brand: Hohner - Quantity: Set of 4 - Country of Manufacture: Germany - Keys: F, A, C, D These have been sitting in a closet. I don't know much about them, so I can't answer detailed questions, but I haven't checked if they produce sound.