Oscilloscope Music
Olin College Principles of Integrated Engineering 2023
What’s an Oscilloscope?
An oscilloscope, or an O-scope as we hear it more commonly referred to, is an instrument capable of visualizing and plotting electric signals. It allows the users to observe the behavior of voltage change over time, which helps when troubleshooting and understanding the behavior of electronic systems. Oscilloscopes are a useful tool in engineering as they are helpful for testing in various situations, from testing to debugging to maintenance of a system.
What is oscilloscope music?
Oscilloscope music is a special type of music that, when plotted on an oscilloscope in X-Y mode, draws images. The X-Y mode plots two signals, in this case the right and left channels of the music, against one another.
This is similar to the concept of a Lissajous figure. The graphic on the right shows a sine wave and a cosine wave, when plotted against one another, form a circle.
Any shape can be plotted on the oscilloscope in this way, but remember that the same signal is also the music, so it needs to sound good as well.
We have created a live performance instrument that produces oscilloscope music in real time. Our instrument outputs audio, which in turn plots the graphics on the oscilloscope display.
How does it work?
This is a diagram of our instrument. It is controlled by a piano keyboard and a pair of knobs (potentiometers). These knobs are the same as the knobs on an etch-a-sketch . While you play notes on the keyboard, you use the knobs to draw the shape the notes make. There is also an erase button to clear the display and a sustain pedal.
Electrical DesignThe inputs, knobs and keyboard, are controlled by an Arduino. The Arduino then sends knob positions and notes to the computer.
Firmware DesignBecause the sound and the image are produced by the same signal, changing the image with the etch-a-sketch knobs also affects the tone of the sound. This signal is generated by software running on a laptop because the processing must be done much faster than would be possible on the Arduino.
Software DesignOur project also includes an alternative visualization mechanism, a laser galvanometer, or galvo. This is a device that deflects a laser beam using a mirror in a similar way to how an oscilloscope draws on its screen. However, because of its nature as a mechanical system, the galvo cannot display signals that are in the audible sound range the way the oscilloscope can. When the galvo is used, the musical aspect is lost.
Mechanical DesignProcess
This project was undertaken in three design sprints. Each sprint focused on a set of goals to be met by the end of the sprint and culminated with an integrated prototype and a sprint review presentation.
Sprint 1
Our first sprint focused on defining our project, laying out the architecture of the product, and building prototype electronics. We constructed a breadboard version of our keyboard and our software gained the ability to draw points on the screen of the oscilloscope.
Sprint 2
We dove into developing laser galvanometers during this sprint. This replaced the keyboard as our primary mechanical objective. The software gained the ability to draw vectors defined by the potentiometer inputs.
Sprint 3
In this sprint, we fully integrated the instrument. The software began taking both vector (knobs) and pitch (keyboard) inputs. The galvanometer project proved to be incompatible with the oscilloscope music aspect, so it was abandoned in favor of a piano keyboard enclosure.
Demo Day
The time before the final demonstration served as an informal fourth sprint. The final keyboard box was designed and built in two days during this time. We added software, firmware, and hardware upgrades to allow for polyphony (playing multiple notes at once), which was a non-trivial challenge.
As part of the PIE course, this project was undertaken with a budet of less than $250. We came in well under that budget, partially by making use of items team members already owned or could borrow.
BudgetMeet the Team
Vaughn Rhinehart
Mechanical Engineer
Interested in learning more about oscilloscope music synthesis and exploring laser galvanometers
Daniel Sudzilouski
Software Engineer
Interested in high-performance C++ code and learning about audio APIs and async patterns.
Ben Kim
Electrical Engineer
Interested in music, sound synthesis, keypad circuit design, and the mathematics of oscilloscope music.
Belén Hutchins
Sustainability Engineer
Interested in learning more about oscilloscopes and their interaction with music and audio synthesis.
Juno Choi
Electrical Engineer
Interested in integration between hardware and software, learning about audio synthesis, and Arduino firmware.