The Instructable that used only a TIP31 power transistor as an LED driver circuit has many problems because it was designed by as 10 years old kid who knows nothing about electronics. It blows up the amplifier, LEDs and TIP31 transistor because it is missing resistors to limit current.
The LM386 can drive an 8 ohm speaker with peak current of 400mA so it is perfect as an LED driver circuit.
Its output pin is normally at half the supply voltage which will light red and yellow LEDs all the time. If a resistor powers a diode at 0.7V then a pot can apply the variable voltage to the inverting input pin of the LM386 to reduce the idle voltage until the LEDs do not light. Then sounds will light the LEDs.
The LM386 acts like a half-wave rectifier so the LEDs are lighted for half the time and their peak current is 40mA but their average current is 20mA.
Try it (I didn't).