Haxophone is an inexpensive and fully customizable electronic musical instrument that resembles a travel saxophone. Under the hood, Haxophone is a particularly elegant (and fun!) Raspberry Pi HAT. The mechanical keys and custom ergonomics give Haxophone a unique and satisfying feel. The design is fully open source, hackable and OSHWA certified. This means that you can make Haxophone entirely your own, from changing the type of key switches to making your own note and instrument mappings. It is a good fit for musicians who are also hackers, or for hackers looking for a fun musical project that won’t break the bank.

While it is not a substitute for a traditional saxophone, Haxophone is accurate enough to allow saxophone players to rehearse both in silence and "on the go". Muscle memory when practicing on Haxophone is transferable to the traditional instrument, and visa versa. This means you can rehearse in all kinds of places that would be unthinkable with a standard saxophone. If it breaks, it is relatively cheap and easy to repair. And, Haxophone is smaller and lighter than any saxophone.

Haxophone has been designed to utilize standard mechanical key switches as fingering keys. In addition of being cool and unique, these are cheaper, more reliable and more repairable than the custom molded keys that you find on digital saxophones.

Hackable Haxophone

Haxophone is purposefully designed to be hackable. Inspect it, modify the fingerings, change the sounds, add features like beats or LEDs. The software is written in Rust, a modern language that has been the most loved code language for the last 7 years (according to Stack Overflow).

Haxophone is designed as a HAT (Hardware Attached on Top) for the Raspberry Pi family of single-board computers. This HAT is a special type of keyboard laid out in the same way that saxophones are. We’ve also designed a mouthpiece and a pressure sensor to detect breath intensity. The HAT includes an audio amplifier, so Haxophone does not need to rely on the amplifier built into the Raspberry Pi 3 and 4. This means the HAT will work with the least expensive of the Pi family, the Raspberry Pi Zero.

Haxophone is fully repairable and customizable. Did you break the thumb rest or would like to use a different color? (3D) print yourself another one. The source models for all 3D printed parts are included in our repository.

Haxophone Design

In order to keep costs down, the Haxophone PCB (printed circuit board) is an integral part of the physical structure of the Haxophone. This means that the key switches, thumb rests, mouthpiece and Raspberry Pi are all attached directly to the PCB. The side keys (left palm and right knuckle keys) are mounted on smaller PCBs and attached to the main PCB via right angle metal brackets. These smaller PCBs are manufactured as detachable panels, bringing down the manufacturing cost.

Keyboard

The keyboard is organized as a 3x8 matrix. The diagram below shows the mapping from saxophone keys to keyboard column/row values.

Note that due to PCB size constraints, a design decision was made to not include a high F# key. This key is not present in all saxophones, as that note can be played using alternate fingerings with other keys. The most common mappings of the high F# are already configured on the haxophone. If you need a less common configuration, the software is easy to extend.

Also note that at the moment the matrix is not completely used: keys (col 0, row 7) and (col 2, row 3) are unused.

Audio Amplifier

Haxophone includes an audio amplifier and a 3.5mm mini-jack. This allows you to connect Haxophone to headphones or an external amplifier.

Haxophone Pinout

The diagram below shows how Haxophone connects to a Raspberry Pi. The keyboard matrix uses discrete GPIOs, the pressure sensor uses I2C, and the audio amplifier uses I2S.

Features & Specifications

• Custom Raspberry Pi HAT PCB
• Software:
  • haxo-rs: This is the driver that detects key presses, breath and converts it into notes. It's written in Rust, and compiled on the Raspberry Pi into a native application
  • fluidsynth: This is the synthesizer software that will convert notes into sounds
• Tactile-feedback 5-pin mechanical switches
• Mechanical keycaps
• Breath pressure sensor
• Built-in audio amplifier (works with no-audio Raspberry Pi's like the Zero and the Zero W)
• Serial console for hacking

Open Source

Our extensive Github Repository contains all of our open source information, including all hardware files, tools/stack, software, manufacturing, BOM, assembly instructions and much more.

Haxophone is Open Source Hardware Association certified with UID PT000005.

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