Audio spectrum analyzer may be a great addition to your music gear. Paul Bishop have build an Arduino based audio spectrum analyzer with NTSC TV out. It enables to see audio spectrum directly on TV screen or… on any screen that accepts this TV standard. He used broken DVD player which also provided a battery power to arduino itself.
video interface is done with only two resistor network DAC which gives a monochrome video signal. Spectrum is displayed in 128×96 resolution. We all know that measuring spectrum relies on Fourier transformation which is quite resource consuming task. Atmega328 has only 2kB of RAM this may be tough task. By using and FFT library on arduino forum he managed to generate 64 band real time video spectrum analyzer. Audio signal is fed from microphone signal amplified with transistor amplifier.