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Show HN: Haxophone (github.com)

526 points by javier_cardona ↗ HN
I built this during Covid. When I released it, some of the parts went out of stock or skyrocketed in price, no longer making this an economic DIY project. Now that things are getting back to almost normal, I thought I'd share it here and request feedback. This is a very niche project for people who like the same things I do: saxophones, Rust, mechanical keyboards and the Raspberry Pi.

75 comments

[ 3.2 ms ] story [ 156 ms ] thread
code_runner
As the owner of a (recently revived) ewi-usb… I’m really curious about the mouthpiece bit. What kind of analog sounds are happening while playing this? Do you notice that reed age, strength etc are as impactful as on a real saxophone? Do you feel a need to swap mouthpieces for different styles of playing?

I love the idea and ingenuity to make this happen!

bwanab
As a sax player who also plays a Roland Aerophone, I have a similar question. Is the mouthpiece a real sax mouthpiece and reed? If so, that means it's making a lot of noise. One of the main appeals of windsynths is that I can play at times when the people in my household (and neighborhood) don't really want to listen to it.

That said, it's a cool project.

javier_cardona
The sounds are synthed sounds (I used fluidsynth) and the haxophone just uses the sound pressure to infer velocity of the notes.

The mouthpiece is optional: you can blow on the neck of the device and will get the exact same sound. But as a sax player, I really prefer to use it with a mouthpiece blowing through it but without making the reed vibrate (so no sound). I find that it helps me maintain proper embouchure and feels more comfortable. And after a solid practice session, I still get that gratifying tingling lower lip feeling.

Thanks for the feedback!

https://github.com/jcard0na/haxo-hw/blob/main/docs/assembly....

tgv
The design says that it measures air pressure. So it's just blowing into a tube, much like e.g. the Yamaha BC-1. I've got one, and in the demo video, I hear the same rapid changes in volume/pressure. I would guess it could benefit from having a small, adjustable opening (like the BC-1), which makes it a bit easier to control.
polishdude20
Yeah and is the pressure sensor closed so you're actually not blowing but just increasing and decreasing pressure?
jcard0na
No, not really. There is sensing tube (which terminates on the sensor) and a venting tube (which lets the air flow through). This is the same technique used in other similar commercial instruments. You can see both tubes in the assembly instructions: https://github.com/jcard0na/haxo-hw/blob/main/docs/assembly....
polishdude20
Ahh that makes sense! So is this actually sensing a lower pressure than ambient? Since moving air results in lower pressure?
jefftk
Reading the assembly instructions it's only an air pressure sensor. You can use a real mouthpiece with reed or not, but it won't make noise actually. It also won't detect anything you do with your mouth.
willcipriano
Needs a reed sensor.
jefftk
If your goal is full fidelity, sure, but they're trying to make a cheap practice device. If you want the former you're probably better off just buying something commercial, at least an AKAI.
amelius
Since it's using keyboard keys I'm guessing it doesn't have any analog touch sensitivity (?) Not sure if that would be even needed on this type of instrument though.
insane_dreamer
It seems the keyboard is pressure sensitive (reference to a pressure sensor in the HW section)
zwkrt
From what I understand of playing a saxophone the variability would come from the mouthpiece. On a type of instrument like a saxophone the valves should always be cleanly opened or closed.
jefftk
Half fingering is a thing, but very rare and fine to be out of scope for a project like this
javier_cardona
Yes, there is no analog touch sensitivity on the sax: keys are either open or closed. The pressure sensor is for volume and note attack.
junon
There exist analog keyswitches, have you considered playing with those?
mkl
I'm really interested in this idea for other DIY instrument purposes.

Razer has keyboards with optical ones, and some people have made them by putting inductive sensors underneath mechanical switches, but I couldn't find any analog keyswitches for sale. Do you have some examples?

How can you deal with a large number of analog inputs to a Raspberry Pi or similar?

junon
I don't remember how many analog input pins exist but a separate circuit that digitizes many analog inputs to a serial stream would be how I'd do it, personally.
jcard0na
While it would be interesting to play with analog keyswitches, it would depart from the experience of a real sax, where the "half pressed" key is of not much use. And it would dramatically increase the complexity of the design.

But the full design is published, just in case anyone wants to try :)

jedimastert
This is also true of the EWI, all of the keys are just metal plates that detect contact, and also generally true of saxophones (although very much not the case with clarinets, which have open finger holes)
klaff
Are there sound samples anywhere?
simlevesque
The video in the repo's readme shows a solo from Stevie Wonder's "Isn't She Lovely"
squarefoot
You can overcome the RPi scarcity by migrating the code to the Teensy platform, which aside being cheaper and less power hungry than the 2,3,4 RPi, is a lot cheaper and more easily available. Not an easy task since there's no Linux under the hood, but there are some excellent audio/midi libraries to help. They already built commercial-level synthesizers with it. By combining the breath sensor data with other pressure sensors you could end up with a very expressive instrument.

https://www.pjrc.com/teensy/index.html

https://www.pjrc.com/teensy/td_libs_Audio.html

https://www.pjrc.com/teensy/td_libs_MIDI.html

https://www.youtube.com/watch?v=z2674LdYW5I

ruleforty
Before I’d do any of that would be vibrato. Without it it is a emotionless keyboard with a blowtube.
code_runner
If I had the knowledge/ability/skills to build an “emotionless keyboard with a blow tube” I’d be pretty damn happy. I don’t think a lack of vibrato diminishes what is going on here.

Am open sourced wind synth made with a custom keyboard? Pretty sick IMO

skybrian
I like Teensy but it looks like their boards are either low-inventory or out of stock too:

https://www.pjrc.com/store/teensy41.html

mftb
I'm not exactly in the target audience, but this is brilliant. Bravo!
tomcam
> This is a very niche project

rockets to #1 on Hacker News

sph
Paraphrasing Frank Zappa, the hacker spirit on this forum is not dead. It just smells funny.
throwaway413
This is one of the coolest things I've seen on HN. I am definitely going to try to follow the instructions on this in the near future! I don't even play saxophone, but now I am not definitely going to learn. I would 100% buy one of these, if not 3 so I could give some as gifts.

Thanks for sharing and seriously, awesome project. Almost brings a tear to my eye.

apienx
So this is how holophonors came about...
xavdid
This is great! As someone who used to play sax a lot but doesn't have hardware experience, it's 100% the sort of thing I would buy if it were commercially available. Makes sense that it's not (ecommerce is a whole thing), but I don't really have the patience to source all the parts and assemble it.

Awesome project though!

matthewhartmans
Love this! Well done OP and thanks for sharing the code!
jader201
The video doesn’t seem to load on iPhone (Safari). It loads a tiny thumbnail, then just spins forever.

Edit: it may be because I’m opening it from the mobile link (which sends the video to Safari), but I tried pulling up the repo directly in Safari, and it shows a whitespace placeholder for the video but that’s it.

WickyNilliams
This is extremely cool. Surprised how good it sounds in the example video. Wish I knew enough about hardware to build one (OK, i also wish i knew how to play sax). Shame there's nobody shipping all the parts for assembly at home. In any case this is awesome, and one of the cooler things I've seen on HN recently!
olivermuty
Can you do a trombone next so we can play trombone hero with a real trombone? :D
wilsonnb3
I bet it would be pretty easy to rig up a PBone or PBone Mini to play trombone hero with
rudolfwinestock
Here are other innovative electronic instruments.

The Eigenharp: https://www.youtube.com/watch?v=9MR5qBtPRrM

The Artiphon Instrument1: https://artiphon.com/pages/instrument1

The Linnstrument: https://www.rogerlinndesign.com/linnstrument

system2
Artiphon videos don't play on the browser. They chose some weird player with unknown host... Why...
wilsonnb3
For those who are more into the “cheap sax like instrument” part rather than the electronic part, you should check out the Yamaha Venova line.
ninjakeyboard
My girlfriend knows how to play the sax and I know rust (and am a dj/producer!) - so I starred this and we plan to build it. Thanks for your contribution to our life!
beau_g
Great work, I am going to fork this into a digital didgeridoo project, or digeridoo for short
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slmjkdbtl
This is so cool! Interesting you can use normal mouthpieces. Curious how the sound works, does the reed need to vibrate like a real saxophone, or you just need to blow into it and some air pressure sensor picks up (forgive me I have no hardware knowledge)?