DIY 555 Analog Synth with 16 step sequencer and simple filtering

I added some simple RC filters to make this thing sound a bit less like a hairdryer fight. The left hand switch turns oscillator 3 on and off. The right switch controls oscillator - switching between a lowpass filter, a highpass/level control and mute. You can see the blue LED for the clock and the 4 red LEDs for the counter off to the right. The two bright LEDs to the left show the note length for oscillators 1 & 2. The two red LEDs to the right of them show the note length for oscillators 3 & 4.