AirBass Lets You Jam Wherever

If you play an instrument, you know how rewarding it is to watch and hear yourself reproduce your favorite songs and make new melodies. But you also know how steep the learning curve can be, how difficult it is to learn positions and notes while your body adjusts to the physical side. For stringed instruments, that means gaining muscle memory, growing fingertip calluses, and getting used to awkward arm positions.

For their final project in [Bruce Land]’s class on designing with microcontrollers, [Caitlin, Jackson, and Peter] decided to make a more accessible bass guitar. For starters, it can be placed flat on a table similar to a pedal steel guitar to get around those awkward arm positions. Instead of plucking or slapping the strings, the player wears a glove with a flex resistor on each finger, and plays the string by curling and uncurling their finger.

We think the team’s implementation of the left hand duties and fretboard is pretty clever. Each of the four strings has a break-beam detection circuit, and a single distance sensor decides where the finger is along the fretboard. Another great thing about this backpack-sized bass is that it never needs tuning. If you stay tuned, you can hear [Peter] play “Smoke On the Water” after the break.

There’s more than one way to make an air guitar — this one that does it with LIDAR.

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Baby’s First Jukebox Is Fun For Parents, Too

Believe it or not, there’s a $400 toy mp3 player out there for kids. It looks pretty nice, with colorful buttons and a wood console and all, but those features don’t really justify the price tag. [DerThes] wanted one for his 2-year-old anyway, so he made his own ruggedized version for a whole lot less.

The simple and kid-friendly interface lets [DerThes Jr.] choose from one of nine albums to play by pushing one of the candy-colored buttons. The bottom row of buttons handle play/pause and moving through the track list. When mom and dad get tired of listening to whatever the kids are into these days, they can enter the special god mode code to access 99 of their favorite albums.

This baby boombox is built with an Arduino Uno and an Adafruit music maker shield. [DerThes] etched his own PCB to hold the buttons and the pair of shift registers needed to interface them with the Uno. If you’ve never etched before, here’s a good chance to dip your toe in the ferric chloride, because [DerThes] has the transparency in his repo and a line on a nice instructional video.

If you don’t think your toddler is ready to respect a field of momentaries, you could make a jukebox with NFC blocks.

[via Arduino blog]

Turning Sounds From A Flute Into Sheet Music

Composing music can be quite difficult – after all, you have to keep in mind all of the elements of musical theory, from time signature and key signature to the correct length for all of the notes. A team of students from Cornell University’s Designing with Microcontrollers class developed a solution for this problem by transcribing sounds from a flute into sheet music.

The project doesn’t simply detect the notes played – it is able to convert the raw audio into a standardized music score complete with accurate note timings and beats per minute. Before transcribing the music, some audio processing was necessary. The team chose to use a Sallen-Key filter to amplify the raw audio input due to its complex conjugate poles. They then used a fast Fourier Transform (FFT) to determine the frequency for the input note, converting the signal from the time domain to the frequency domain.

The algorithm samples the data to generate an input signal, using the ADC on the microcontroller to receive input from the microphone. It takes the real and imaginary components of the sampled signals and outputs a pair of real and imaginary amplitude components corresponding to the sampled frequency, evenly spaced from 0 to the Nyquist rate (half the sampling rate). The spacing of these bins and the bin with the largest amplitude are used to convert the signal back to a real frequency and a MIDI note.

The system uses a PIC32 for the logic. The circuitry for the microphone amplification uses a non-inverting op-amp with a gain of 50 to increase the microphone output signal amplitude from 15 mV to 750 mV to use by the microcontroller’s ADC. The signal is then sent to the anti-aliasing Sallen-Key filter, with a pole at 2.5 kHz and a Q of 1. The frequency was chosen since the FFT samples at 8 kHz and the frequency corresponds to a note out of the range of a flute. As for the filters, only the low pass filter was implemented in hardware.  While a bandpass filter could have been implemented in hardware, the team decided on a cleaner software approach.

The project is well-documented on the team’s project page, and it’s certainly worth checking out for more detailed discussions on the keypad controls and the software side of the audio processing. If you want to learn more about the FFT, check out this 2016 Hackaday Prize entry for an FFT spectrum analyezer.

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Need Hackable Melodies? Here’s The TETRIS Theme And More

[Robson Couto] started to get interested in musical projects and as a side effect created downloadable code with simple notation for a good variety of themes, songs, and melodies. They are all for the Arduino and use only the built-in tone() function, but don’t let that distract you. If you look past that, you’ll see that each sketch is a melody that consists of single notes and durations; easily adapted to other purposes or simply used as-is. After all, [Robson] wanted the source of each tune to be easily understood, easily modified, and to have no external dependencies.

All that may sound a bit like MIDI, but MIDI has much more in common with hardware events than music notation because it includes (among other things) note starts and note ends as separate elements. Converting MIDI into a more usable format was a big part of a project that fed Bach music to a neural network and got surprisingly good results.

When doing music projects, sometimes having a recognizable melody represented very simply as notes and durations with only one note at a time can be an awfully handy resource, and you can find them on GitHub. There’s a brief video of the Tetris theme (actual name: Korobeiniki) being played after the break.

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[Fran] Is Helping Santa Slay This Year

We know at least one person who ought to make Santa’s ‘nice’ list this year. [Fran] was probably near the top of it already, but sending Santa a handmade greeting card with a fully-functioning guitar amp inside will probably make him rewrite her name in glitter, or silver Sharpie.

This stocking stuffer-sized amp is based around the LM386 and the bare minimum components necessary to make it rock. Everything is dead-bug soldered and sandwiched between two pieces of card stock. The first version with a single 386 sounded okay, but [Fran] wanted it louder, so she added another stage with a second 386. [Fran] glued the rim of the speaker directly to the card so it can act like a cone and give a better sound than the speaker does by itself.

All Santa needs to rock out is his axe and a small interface made of a 1/4″ jack and a 9 V wired to a 3-pin header that plugs into the card. He can take a break from Christmas music and let some of those cookies digest while he jams. Be sure to check out the build video after the break if you want to stay off the ‘naughty’ list.

Want to make your own musical greeting card? If you can program an ATtiny85, you won’t need much more than that to send a smile. If visual art is more your thing, 3D print them a 2D picture.

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Bottle Organ Breakdown

A keen-eyed commenter pointed us to a homemade bottle organ that plays like a piano. The complexity gets turned up with foot-powered bellows and custom keys, but the magic of [Mike] and [Simon Haisell]’s garage-built instrument is not lost in the slightest. We also have the video below the break and there is a bottle organ performance by [Coyote Merlot].

The working concepts are explained well in the video, and that starts with the bellows. In the first few seconds of the video, we see an organist swaying as he plays, and it would be accurate to say the music moves him. The wobbling is to pedal a couple of levers that squeeze a pair of air sacs and slide under wheels that look like a hardware store purchase. The spring-return mechanism is a repurposed bungee cord and you know we dig that kind of resourcefulness. Each bellow valve is made with traditional leather flaps of the type that predate bungee cords and camera phones. These air pumps inflate a big reservoir in the back that provides continuous pressure to a manifold where each of the thirty-six keys control a valve responsible for one bottle. The pair built every wooden part we mentioned with the explicit purpose of creating this organ.

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Programmable Wrist Synth Pushes The Envelope

Synths are a ton of fun no matter how good or bad they sound. Really, there are no bad-sounding ones, it’s just that some are more annoying to listen than others to if you’re not the one making the beep boops. [Clem] had built a tiny LDR-based synth into a watch case a few years back and took it to many a Maker Faire, where it delighted and annoyed until it ultimately broke.

Naturally, it was time to make a new version that’s more capable. Whereas the first one was Atari-punk-console-meets-light-Theremin, this one has a bunch of inputs and can be programmed on the fly to record and play back bendable tones. It’s driven by an Arduino MKR, and the inputs are managed by an impressively squash bug-wired shift register. [Clem] used beefy switches this time in the hopes that this one will last longer. We think the slide pots are a great touch, as are the candy-colored knobs printed in PMMA.

Our favorite part is that [Clem] took advantage of the random states the microcontroller pins are in when it’s first powered on. If you don’t want to program any notes, you can use the ones generated at boot and just play around with those. Be sure to check out the build video after the break.

We’ve seen our share of synths, but few as delicious-looking as KELPIE from this year’s Hackaday Prize.

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