Check out this DIY Hypnotic Synthesizer Acid Machine that will allow you to hypnotize anyone or at least let them feel “high” on some music notes.
The circle with the lines that you see on the top of the machine, rotates and displays the note you are playing.
When you play a C the lines in the middle circle will be standing still.. from the C it will go outward, displaying all notes on a keyboard in 12 steps.
It works by making a LED blink in the frequency of the sound, and rotating the image at a set speed. For the distance between the lines i used this table, it displays musical frequencys in centimeters.