For more than a century, these double-sided harmonicas have been a player favorite. Two keys are available on each individual instrument. The Echo´s precision tuned reeds create a beautifully blended vibrato tone. The double row of holes on Tremolo Harmonicas creates music with a distinctive vibrating (vibrato) effect. This is produced by the bottom row of holes and the top row of holes being played at the same time and tuned to the same note, with the top row tuned just slightly higher. This special tuning enables the player to make the tremolo sound which is especially popular for ballads, gospel and folk music. Due to health regulations this item cannot be returned. Key of C/G. Hohner's tremolo harmonicas are double reed instruments. The bottom row of holes features the same notes as the top row, tuned slightly higher. This special tuning creates the tremolo's distinct sound, a beautiful vibrato effect with a richer tone. These harmonicas are primarily used in ballads, folk, reggae & gospel music.