The Echo Double Sided series has been a favorite since the turn of the century. Beautifully stamped covers enclose the reeds of this tremolo model and provide a common tone chamber. This reinforces sympathetic resonance between the sides and lends a deep, haunting quality to the music. Tremolo harmonicas are Diatonic models constructed with double holes, each containing two reeds tuned to the same note, one tuned slightly higher than the other. Since both reeds are either blow or draw, when played both will sound together - the slight difference in tuning creating a beautiful vibrating or tremolo effect. Tremolo models are popular for ballads and gospel music, as well as for Latin, Asian, European and other international folk styles.