FutureGrab is a new wearable musical instrument for live performance that is highly intuitive while still generating an interesting sound by subtractive synthesis. Its sound effects resemble the human vowel pronunciation, which were mapped to hand gestures that are similar to the mouth shape of human to pronounce corresponding vowel. FutureGrab also provides all necessary features for a lead musical instrument such as pitch control, trigger, glissando and key adjustment. In addition, pitch indicator was added to give visual feedback to the performer, which can reduce the mistakes during live performances. This paper describes the motivation, system design, mapping strategy and implementation of FutureGrab, and evaluates the overall experience.