A FM stereo modulator is disclosed and claimed for modulating/converting the audio output signal of a portable music player into a FM signal receivable by the FM tuner of a stereo system. It comprises an electrically insulating hollow enclosure, a power connector connected by a first cable to one end of the enclosure for connection to external power supply, a music source connector connected by a second cable to the other end of the enclosure which is connectable to the audio output terminal of a portable music player, and a FM modulating circuit mounted inside the enclosure and electrically connected to the power connector and to the music source connector for modulating the audio output signal of the portable music player connected to the music source connector into FM tuner receivable radio signal with one of carrier frequencies selected by the user.