How to make a LED flash together with the music BPM

Just a simple idea, so I am not sure but you'd probably need to pass the signal through a Low Pass filter since the beat is at low frequencies of the audio spectrum and then you could feed it to a BJT that controls the current passing through the LED.

Regards

Google for "color organ". These usually have 3 or more frequency bands, but you will get the idea. Just build the low band if you only want the bass beat.

Best regards,

Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!