Abstract: A hand-muscle developer including a casing, a strap for fastening the casing to the hand, a music IC circuit board installed inside the casing, a speaker mounted on the casing and connected to the music IC circuit board, a battery power supply to provide power supply to the music IC circuit board, a plurality of melody keys mounted on the casing and respectively depressed by fingers to make electrical contact for triggering the music IC circuit board to produce a specific tone through the speaker, and a tuning means mounted on the casing and controlled by the thumb to tune the tones triggered by the melody keys.