The Tremolo-Harp is a twelve-stringed robotic instrument, where each string is actuated with a DC vibration motor to produce a mechatronic "tremolo" effect. It was inspired by instruments and musical styles that employ tremolo as a primary performance technique, including the hammered dulcimer, pipa, banjo, flamenco guitar, and surf rock guitar. Additionally, the Tremolo-Harp is designed to produce long, sustained textures and continuous dynamic variation. These capabilities represent a different approach from the majority of existing robotic string instruments, which tend to focus on actuation speed and rhythmic precision. The composition Tremolo-Harp Study 1 (2019) presents an initial exploration of the Tremolo-Harp's unique timbre and capability for continuous dynamic variation.