Function Generator Music in 5 Minutes / by Daniel Ehrman

Forget oscilloscopes. Ever wondered what it sounds like to play a function generator through a guitar amp?

In my undergrad, while working on the Purdue Solar Racing team back in 2011, I borrowed the team's function generator when it wasn't in use and carried out some "musical experiments" back at home.

I have a Fender Cyber Champ amp, which has a whole host of effects built in: phaser, flange, chorus, various kinds of reverb, and a lot more. So the thought was that if I could combine a box of essentially unlimited sounds with these spacey guitar effects, I could cook up some pretty cool live music, or at the very least, synthesized effects to lay over whatever other music I was working on at the time.

Of course I eventually had to give back it back, but I never stopped thinking about all of the unique sounds I could make with that function generator. I'd once seen a documentary on the making of The Dark Side of the Moon, and the idea of crafting an entire composition from little hand-made sonic components truly lit a fire in my engineer's brain.

Back to the present day.

Last week, I finally ordered my own function generator for $25 on eBay and started right where I left off three years ago.

 Clockwise from top left: (1) GW GFG-8015G function generator, (2) Boss RC-2 Loop Station, (3) Fender Cyber Champ amp, (4) Presonus AudioBox USB interface, (5) headphones, (6) PC.

Clockwise from top left: (1) GW GFG-8015G function generator, (2) Boss RC-2 Loop Station, (3) Fender Cyber Champ amp, (4) Presonus AudioBox USB interface, (5) headphones, (6) PC.

The diagram above shows the final setup with all of the required pieces for recording the music. The loop station (top center) is the key: it lets me loop back what I've previously recorded without the help of a computer so I can compose everything live in one shot. The computer in the diagram, and in fact the entire bottom row, is only present for recording purposes.

Also note that technically, you would want any effects—including the amp—placed before the looper so that different effects could be saved with each track rather than the same effects being applied to the entire composition, but I just wanted a quick and simple setup here. The only effects I actually used were very small amounts of reverb, delay, and chorus.

I start with a 2 Hz square wave with a non-50% duty cycle to create a heart-beat-like bass drum. (Listen to this beginning section of Dark Side for comparison.) Typically, this wouldn't be audible due to its being below the 20 Hz human hearing cutoff, but the quick changes in the line level create some residual precussive frequencies that we can hear quite well.

Then, in remembering the repetitive, but beautiful, two-chord droning of Pink Floyd's "Breathe," I set the frequency knob to A for four beats and E for four beats. (Note: it seems like these notes all came out half a step lower, which I'll have to investigate further.)

With the basic notes down, I start overlaying more of the notes that comprise the A major and E minor chords, with the pleasant surprise of some phaser effect as I double-record the same, but phase-shifted, notes.

Add on top of that a couple "slides" into notes and some (admittedly atonal) quickly changing frequencies, and we're pretty much done.

So here's the final 15-second composition (that loops ad infinitum):

Ultimately, I have much bigger plans for this function generator, but this is a nice kick-off to what will hopefully become a seriously fun audio engineering project.