Drive LEDs in a bar from an amplifier output?
The standard part for this task is the LM3914 ("Dot/Bar Display Driver"). It functions as a multitap voltage divider, and compares the signal with the value at each tap:



The easiest way to build this will be to simply use a LM3914 for each graph. The pinout of this part is such that you can directly drive a 10-segment bar graph LED from the chip. If this is too easy for you, you can try building an equivalent circuit yourself, but you'll need a lot of comparators to make it work.