This is a step sequencer I made with an Arduino. There's 1 button for each step, holding the button sets the pitch of that note. (Ideally each note would have its own slide potentiometer but the Arduino I have only has 6 analog input pins so I had to improvise.) Sliding the potentiometer sets the pitch of the note you're changing. The right knob sets the tempo, and the left knob increases the amount of a weird under/overtone effect I made, which one of my housemates unlovingly deemed the "Clown Funeral" effect. I made this using the freqout function and some debugging help from Beavis Audio's Arduino Punk Console.