Tremolo harmonicas are diatonic models constructed with double holes, each containing two reeds tuned to the same note. Each reed is tuned slightly higher than the other and, when played together, this slight difference in tuning creates a beautiful vibrato or tremolo sound. With beautifully constructed models to suit any style and budget, from the pocket sized Humming Mate through to the premium-tier SCT-128, there is a tremolo harmonica for everyone in this superb collection.