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.

Needs a reed sensor.

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.

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.

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!

Very cool! Awesome project

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.

Yeah and is the pressure sensor closed so you're actually not blowing but just increasing and decreasing pressure?

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....

Ahh that makes sense! So is this actually sensing a lower pressure than ambient? Since moving air results in lower pressure?

Looks like just a pressure sensor. You might be interested in the KontinuumLab channel, from a guy who has done EWI projects with more sensors.

https://www.youtube.com/@KontinuumLAB

Most recently: https://youtu.be/1CXjADjIM1s