The Mystery Of The Messed-Up Hammond X5

[Filip] got his hands on a sweet old Hammond X5 organ, but it had one crucial problem: only half of the keys worked. Each and every C#, D, D#, E, F, and F# would not play, up and down the keyboard, although the other notes in between sounded just fine.

Those of you with an esoteric knowledge of older electric organs will be saying “it’s a busted top-octave generator chip”, and you’re right. One of the TOGs worked, and the other didn’t. [Filip] rolled his own top-octave generator with a Pico, in Python no less, and the old beauty roared to life once more.

But what is a top-octave generator, you may ask? For a brief period of time in the early 70s, there were organs that ran on square waves. Because a musical octave is a doubling or halving of frequency, you can create a pitch for every key on the organ if you simply create one octave’s worth of pitches, and divide them all down using something as simple as a binary counter IC. But nobody makes top-octave chips any more.

Back in 2018, [DC Darsen] wrote in asking us if we knew about any DIY top-octave designs, and we put out an Ask Hackaday to see if you all could make a top-octave generator out of a microcontroller. We got a super-optimized code hack in response, and that’s worth checking out in its own right, but we always had the nagging suspicion that a hardware solution was the best solution.

We love how [Filip]’s design leans heavily on the Pico’s programmable input/output hardware modules to get the job done with essentially zero CPU load, allowing him to write in Python and entirely bypassing the cycle-counting and assembly language trickery. The voltage shifters and the switchable jumpers to swap between different top-octave chip types are a nice touch as well. If you have an organ that needs a top-octave chip in 2024, this is the way we’d do it. (And it sounds fantastic.)

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Virginia Cave Is The Largest Musical Instrument In The World

Hit something with a hammer, and it makes a sound. If you’re lucky, it might even make a pleasant sound, which is the idea behind the Great Stalacpipe Organ in Luray Caverns, Virginia. The organ was created in 1954 by [Leland W. Sprinkle], who noticed that some stalactites (the ones that come down from the ceiling of the cave) would make a nice, pure tone when hit.

So, he did what any self-respecting hacker would do: he picked and carved 37 to form a scale and connected them to an electronic keyboard. The resonating stalactites are spread around a 3.5 acre (14,000 square meters) cave, but because it is in a cave, the sound can be heard anywhere from within the cave system, which covers about 64 acres (260,000 square meters). That makes it the largest musical instrument in the world.

We’ll save the pedants the trouble and point out that the name is technically an error — this is not a pipe organ, which relies on air driven into resonant chambers. Instead, it is a lithophone, a percussion instrument that uses rock as the resonator. You can see one of the solenoids that hits the rock to make the sound below.

This is also the sort of environment that gives engineers nightmares: a constant drip-drip-drip of water filled with minerals that love to get left behind when the water evaporates. Fortunately, the Stalacpipe Organ seems to be in good hands: according to an NPR news story about it, the instrument is maintained by lead engineer for the caverns [Larry Moyer] and his two apprentices, [Stephanie Beahm] and [Ben Caton], who are learning the details of maintaining a complex device like this.

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2023 Halloween Hackfest: Organ-playing Skeleton Livens Up Halloween

Every hacker appreciates how off-the-shelf parts can be combined into something greater, and [bryan.lowder] demonstrates this beautifully with his organ-playing skeleton, a wonderful entry to our 2023 Halloween Contest!

Skelly the 3-foot-tall novelty skeleton animatedly plays Bach’s Toccata and Fugue in D Minor while perched at an old (and non-functional) Hammond organ. The small animatronic skeleton has canned motions that work very well for mock organ playing while an embedded MP3 player takes care of playing the music.

That’s not to say the project didn’t have its challenges. Integrating off-the-shelf components into a project always seems to bring its own little inconveniences. In this case, the skeleton the MP3 player both expect to be triggered with button pushes, but taping the button down wasn’t enough to get the skeleton moving when power was applied. [bryan] ended up using relays to simulate button pushes, and a 555 timer circuit to take care of incorporating a suitable delay.

As [bryan] puts it, “a technical tour de force it ain’t, but it is practical and it works and it was done on time” which is well said. Watch Skelly in action in the video, embedded below. There’s also a second video showing the homebrewed controller and MP3 player, both concealed under Skelly’s robe.

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Horror Instrument Is Truly Astounding To Listen To

Truly new musical instruments don’t come along every day; much of the low hanging fruit has already been taken. [Simon the Magpie] has been working on something that’s just a little innovative, and built what he refers to as an “Incredible Horror Instrument.” It’s all about feedback.

The build started with the Suzuki Andes 25F, a so-called “keyboard recorder.” It has the appearance of a melodion but produces flute-like sounds. [Simon]’s idea was to combine the breath-powered instrument with a talk box. If you’re unfamiliar, a talk box is designed for playing amplified guitar sounds through a tube that is placed in a player’s mouth so they can “shape” the guitar sound with their mouth.

In this role, though, the talk box’s input is hooked up to a microphone which captures the output of the Andes 25F. It then plays this back through a tube connected to the breath input of the Andes 25F. [Simon] thus created a feedback look that can effectively be “played” via the keyboard on the Andes 25F.

The audible results are eerie and haunting, and seem more than fitting for even a well-budgeted horror film. [Simon] also demonstrates some neat possibilities when combining the setup with a further feedback loop that feeds in other tones.

We’ve covered [Simon’s] work before; it’s often noisy and always entertaining. Video after the break.

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This Found-Sound Organ Was Made With Python And A Laser Cutter

Some readers will no doubt remember attaching a playing card to the front fork of their bicycle so that the spokes flapped the card as the wheel rotated. It was supposed to sound like a motorcycle, which it didn’t, but it was good, clean fun with the bonus of making us even more annoying to the neighborhood retirees than the normal baseline, which was already pretty high.

[Garett Morrison]’s “Click Wheel Organ” works on much the same principle as a card in the spokes, only with far more wheels, and with much more musicality. The organ consists of a separate toothed wheel for each note, all turning on a common shaft. Each wheel is laser-cut from thin plywood, with a series of fine teeth on its outer circumference. The number of teeth, as calculated by a Python script, determines the pitch of the sound made when a thin reed is pressed against the spinning wheel. Since the ratio of teeth between the wheels is fixed, all the notes stay in tune relative to each other, as long as the speed of the wheels stays constant.

The proof-of-concept in the video below shows that speed control isn’t quite there yet — playing multiple notes at the same time seems to increase drag enough to slow the wheels down and lower the pitch for all the notes. There appears to be a photointerrupter on the wheel shaft to monitor speed, so we’d imagine a PID loop to control motor speed might help. That and a bigger motor that won’t bog down as easily. As for the sound, we’ll just say that it certainly is unique — and, that it seems like something [Nicolas Bras] would really dig.

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The Quadrivium EnsembleBot Is A Labour Of Love

The Quadrivium EnsembleBot project is a mashup between old school musical instruments and the modern MIDI controlled world. Built by a small team over several years, these hand crafted instruments look and sound really nice.

The electronics side of things is taken care of with a pile of Arduinos and off-the-shelf modules, but that doesn’t mean the design isn’t well thought through, if a little more complicated than it could be in places. Control is taken care of with a PC sending commands over the USB to an Arduino 2560. This first Arduino is referred to as the Master Controller and has the immediate job of driving the percussive instruments as well as other instruments that are struck with simple solenoids. All these inductive loads are switched via opto-isolators to keep any noise generated by switching away from the microcontroller. A chain of four sixteen-channel GPIO expander modules are hung off the I2C bus to give even more opto-isolated outputs, as even the Arduino 2560 doesn’t quite have enough GPIO pins available. The are a number of instruments that have more complex control requirements, and these are connected to dedicated slave Arduinos via an SPI-to-CAN module. These are in various states of development, which we’ll be keeping our beady eyes on.

One of the more complex instruments is the PipeDream61 which is their second attempt to build a robotic pipe organ. This is powered by a Teensy, as they considered the Arduino to be a little too tight on resources. This organ has a temperature controller using an ATTiny85, in order to further relieve the main controller of such a burden and simplify the development a little.

Another interesting instrument is Robro, which is a robotic resophonic guitar which as they say is still work in progress despite how long they have been trying to get it to work. There’s clearly a fair bit of control complexity here, which is why it is taking so much fiddling (heh!) to get it work.

This project is by no means unique, lately we’ve covered controlling a church organ with MIDI, as well as a neat Arduino Orchestra, but the EnsembleBot is just so much more.

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Polyphony On A Tiny Scale

Older readers may remember the Stylophone, a small battery powered electric organ using conductive PCB pads and a stylus to create notes. The simple multivibrators in those instruments made them monophonic, but here in 2021 we can do better than that! [Sjm4306] has gone the extra mile with a PCB organ, by making a capacitive-touch instrument that boasts four-note polyphony.

At its heart is an ATmega328p whose software sports four tone generators that each emerge on a different pin. These are summed using a set of 100 Ω resistors and fed to a tiny speaker. Power comes from a CR2032 lithium cell, and he notes that a higher voltage delivers more volume.

The full story is detailed in the video below the break, along with a bit of four-note polyphonic action. We’re guessing that this instrument would sound sensational when hooked up to a reverb unit.

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