The Mysterious Barrier is a timpani duet written for nine drums. The timpani are arranged in a circle, facilitating easy movement of the players between two sets of four drums which are joined by a single piccolo timpani. This is Kirk J. Gay’s follow-up to Fear Cage which uses the same timpani setup. The thematic material for the piece is taken from François Couperin’s harpsichord work Les Barricades Mystérieuses, which comes from Ordre de Pieces de Clavecin, a collection of harpsichord works by Couperin. The two timpani parts work together to recreate the melodic and harmonic structures from Couperin’s work. In addition to working together in overlapping harmonies, the timpanists also split complex and fast rhythms to imitate arpeggios and runs on the harpsichord. There are also sections where the two players trade phrases back and forth, which creates different harmonic movements than the other techniques in the piece. This virtuosic and showy piece will give percussionists and timpani afficionados a great vehicle to entertain crowds, and create something unique with two sets of drums. This piece comes as a professionally printed and bound score and includes individual parts in PDF format for printing or for tablet viewing.