The circuit given above is not feasible. First of all, connecting an external circuit to the signal output to the speaker will affect the signal noise and sound quality. Secondly, the signal output to the speaker is a voltage or power signal, and the switching tube has it. At a certain conduction voltage, if it is higher than the conduction voltage, the light will be on, and if it is lower than the light, the light will be dark, and the light will not change in brightness. Moreover, if there are many musical instruments and the signal band is wide, the flickering of the light will not reflect the rhythm of the music at all.

It is not feasible to simply build a circuit to achieve this. You need to use a microcontroller to segment and resample the high, middle and bass sounds to the microcontroller. The microcontroller analyzes the sampled voltage signal and then outputs a certain current or brightness to the LED.< /p>

It depends on where you use it. In fact, some people who play HIFI have such sampling kits for sale. Go to some music forums to find what you should have.