How To Build A Car Horn Organ, Part One: The First Part

As I've mentioned here before, cars are incredible mobile colonies of amazing parts that can be repurposed for any number of uses. One of those uses can be annoying people in an entire neighborhood at once, which I suspect will be the main result from this week's project: the car horn organ.

Yep, we're going to show you how to make an organ. Out of horns. You're welcome (your neighbors, not so much).


Playing car horns outside of cars has probably been happening, informally, ever since there were enough cars to have junkyards. But the idea of an actual instrument from car horns has an inventor, Wendy Mae Chambers. Chambers first built her car horn organ in 1983, and has managed to use it to annoy people all over the globe. She uses a 25-horn organ. Our goals are more modest— we'll just try for a 7-horn organ (at first) and only try to annoy the surrounding block around my house.

Technically, a car horn organ is quite simple. I've drawn the basic diagram up above, but essentially it's a simple circuit for each horn. Each horn has its ground terminal connected to the negative pole of the battery (or, really any 12V power source), and the hot lead from the horn is connected to a switch of some kind, then from the switch on to the positive battery/power source terminal.

I'm planning on using an old synthesizer keyboard for the switches, using one octave of the keyboard. Maybe I can find a one-octave kid's toy keyboard. As long as it's something that someone with some sort of musical skills can play, that's good enough.

So, the plan is simple enough, technically. The real challenge with a car horn organ is sourcing the notes themselves. Even with my modest goal of just seven notes (A-G), this proved tricky. To do this, I enlisted the help of my friend Chris Kallmyer, a great musician who was willing to trek out in August California desert junkyard heat to find the right horns.


We went to a junkyard with the battery from my truck, some tools, a way to mark the horn's notes, and an iPhone (or Android) app that can produce pitches. You can also use a pitch pipe, or year ears if you're one of those freaks who can do that sort of thing.


I'm a musical nincompoop (though I love making noise), so I relied heavily on Chris to identify the pitches of the horns. The good news is horns are usually left on junkyard cars. The bad news is they're often so corroded and rusted that getting them off is a much bigger chore than you'd think. Be patient, and try not to get tetanus.

So far, we found an A, B, two Cs, E, F, and F#. We found some sharps and flats as well, but are focusing just on the basics for now. A seems most common, but I'll get a full report later. Some cars use multiple horns to make a small chord— make sure to try both. Try all kinds of cars. Americans tend to go for deeper and louder, Asian cars seem to like higher pitches, and I think we got the E from a Peugeot. Most euro cars go for funny, flat pitches, it seems. I'll do a post at some point about exactly what all that means.


There may be ways to tune the horns with voltage adjustments or other means. Chris has said he has an idea, which we'll explore in part two when we get this thing put together. After it's done, the goal is to get a real musician to try and play something recognizable. If I can pull it off, I'll have video.


So, stay tuned and hopefully I'll be having neighbors calling in noise complaints on me very soon!

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