Craig Lindley is a technical author and a prolific maker of things. This simple project was his first attempt to create a laser harp MIDI device. While on vacation, Craig saw a laser harp with only three strings and decided to improve upon it by expanding it to twelve strings. The principle of operation is straightforward: twelve cheap diode laser modules aim a beam towards an LDR, which changes resistance if the light level changes when the beam is interrupted.

The controller is a simple piece of perf board, with a Wemos D1 mini ESP32 module flanked by some passives, a barrel socket for power, and the usual DIN connector for connecting the MIDI instrument. Using the ESP32 is a smart choice, removing all the need for configuration and user indication from the physical domain and pushing it onto a rarely-needed webpage. After a false start, attempting to use a triangular frame arrangement, [Craig] settled upon a simple linear arrangement of beams held within a laser-cut wooden box frame. Since these laser modules are quite small, some aluminium rod was machined to make some simple housings to push them into, making them easier to mount in the frame and keeping them nicely aligned with their corresponding LDR.

Sadly, the magnetic attachment method [Craig] used to keep the LDRs in place and aligned with the laser didn’t work as expected, so it was necessary to reach for the hot glue. We’ve all done that!

An interesting addition was using an M5 stack Unit-Synth module for those times when a proper MIDI synthesiser was unavailable. Making this luggable was smart, as people are always fascinated with laser harps. That simple internal synth makes travelling to shows and events a little easier.

Laser harps are nothing new here; we have covered plenty over the years. Like this nice build, which is more a piece of art than an instrument, one which looks just like a real harp and sounds like one, too, due to the use of the Karplus-Strong algorithm to mimic string vibrations.

If you missed the introduction of the Axis-49 and Axis-64 keyboards by C-Thru Music, you’re definitely not alone. At the time it was a new musical instrument that was based on the harmonic table, but it launched during the Great Recession and due to its nontraditional nature and poor timing, the company went out of business. But the harmonic table layout has a number advantages for musicians over other keyboard layouts, so [Ben] has brought his own version of the unique instrument to life in his latest project.

Called the Midihex, the keyboard has a number of improvements over the version from C-Thru Music, most obviously its much larger 98 playable keys and five function keys. The keys themselves are similar to Cherry MX keys but which use Hall-effect sensors. This style of key allows the device to send continuous key position information to the host computer, and since this is a MIDI instrument, this capability allows it to support a MIDI protocol called MIDI Polyphonic Expression (MPE) which allows each note to be more finely controlled by the musician than a standard MIDI instrument. The PCB is powered by a Teensy 4.1 at the core.

For any musicians that haven’t tried out a harmonic table before, an instrument like this might be worth trying out. The layout provides easier chord and scale patterns, and for beginner musicians it can have a much shallower learning curve than other types of instruments. If you can’t find an original Axis-49 or Axis-64 anywhere to try out, though, we actually posted a teardown of one way back in 2009 when the company was still producing instruments.

The progress for electronics over the past seven decades or so has always trended towards smaller or more dense components. Moore’s Law is the famous example of this, but even when we’re not talking about transistors specifically, technology tends to get either more power efficient or smaller. This MIDI keyboard, for example, is small enough that it will fit in the space of a standard business card which would have been an impossibility with the technology available when MIDI first became standardized, and as such is the latest entry in our Business Card Challenge.

[Alana] originally built this tiny musical instrument to always have a keyboard available on the go, and the amount of features packed into this tiny board definitely fits that design goal. It has 18 keys with additional buttons to change the octave and volume, and has additional support for sustain and modulation as well. The buttons and diodes are multiplexed in order to fit the IO for the microcontroller, a Seeed Studio Xiao SAMD21, and it also meets the USB-C standards so it will work with essentially any modern computer available including most smartphones and tablets so [Alana] can easily interface it with Finale, a popular music notation software.

Additionally, the project’s GitHub page has much more detail including all of the Arduino code needed to build a MIDI controller like this one. This particular project has perhaps the best size-to-usefulness ratio we’ve seen for compact MIDI controllers thanks to the USB-C and extremely small components used on the PCB, although the Starshine controller or these high-resolution controllers are also worth investigating if you’re in the market for compact MIDI devices like this one.

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Pianos traditionally had keys made out of ivory, but there’s a great way to avoid that if you want to save the elephants. You can build a keyboard using spoons, as demonstrated by [JCo Audio]. 

The build relies on twelve metal spoons to act as the keys of the instrument. They’re assembled into a wooden base in a manner roughly approximating the white and black keys of a conventional piano keyboard, using 3D-printed inserts to hold them in place. They’re hooked up to a Raspberry Pi Pico via a Pico Touch 2 board, which allows the spoons to be used as capacitive touch pads. Code from [todbot] was then used to take input from the 12 spoons and turn it into MIDI data. From there, hooking the Pi Pico up to a PC running some kind of MIDI synth is enough to make sounds.

It’s a simple build, but a functional one. Plus, it lets you ask your friends if they’d like to hear you play the spoons. The key here is to make a big show of hooking your instrument up to a laptop while explaining you’re not going to play the spoons a la the folk instrument, but you’re going to play a synth instead. Then you should use the spoon keyboard to play emulated spoon samples anyway. It’s called doubling down. Video after the break.

Have you ever wanted to take a break from reading or studying to just rock out for a few blissful minutes? If you’re anything like us, you like to rock out most of the time and take the occasional break to do your reading. Either way, you really can’t go wrong with this MIDI bookmark from [Misfit Maker].

This slick little bookmark may look 3D printed, but it’s all carefully-cut foam board in two thicknesses. Even the keys are made foam board — they’re just wrapped in carbon fiber so they look extra cool.

Underneath that carbon fiber is a layer of aluminium tape to make them capacitive. [Misfit Maker] recommends using copper tape instead because it allows for wires to be soldered directly to the keys.

The brains of this beauty is in the form of an ESP32 which is controlling an MPR-121 capacitive touch sensor. If you’d like to make one of these for yourself, there are plenty of helpful GIFs embedded in the thorough write-up. Be sure to check out the brief demo after the break.

If you want to easily MIDI-fy something and use touch inputs, you can’t really go wrong with the Raspberry Pi Pico, which does capacitive touch natively. Check out this MIDI kalmiba to learn more.