Bending takes a bit of practice but it’s not terribly hard. Here are some general tips for absolute beginners that are based simply on my anecdotal experience as an amateur player:

1. Don’t start with a wooden harp like marine band. The metal and plastic ones are typically a bit easier to bend.

2. One hole at a time. Ensure you can exclusively blow in a single hole to practice

3. Lower notes are generally easier to bend than higher notes

4. Make an O with your mouth and have the tongue float in the middle. Start by pulling, not pushing, in my experience bending on intake is slightly easier than bending on blowing out.

5. Tighten the lips and decrease the size of the O to increase pull force on the reed to create a bending effect, and also tighten the airflow chamber above your tongue by pulling your tongue back and up, then loosen it by moving your tongue forward and down

This tool looks great for helping improve once you’ve been able to perform the initial bend. Excited to try it out!

I love to see that you've added overbend targets! Overblowing is one of my more favorite things to do on the harmonica, but due to it being an advanced technique it's often overlooked.

I love seeing projects that shed a little vignette on a wide world I had no idea about! Thanks for posting!

When I was learning bending, I like the app "Bending Trainer" available for both Android and iOS, with a blue on black icon

I suppose your target audience knows what “bending” means, but I had to google it after visiting your site. Maybe a sentence or two on your site explaining what bending is, or a demonstration on your intro video, would be helpful.

This is great. Would have loved it when I used to have fun with the harmonica.

Here is a suggestion. Display a graph of played-frequency vs time. Then I can compare visually how my bending performance improves over time.

Harp player here. When I first started playing, I had a Gindick's book, Country and Blues Harmonica For the Musically Hopeless. This was maybe 35 years ago. I would recommend that book and the tape (cd? mp3?) that comes with it, for beginners. You can't see the notes you are playing on a harmonica. You have to hear them. You start by playing clear single notes and then shaping the note by articulating eeeh-yah or something similar and the note magically bends. You have to hear the note so you can tell if the note bends. It is very organic, and I don't think an app will help much. It may confirm what is happening, but it is not going to help if you can't do it. Personally, I played along with Little Walter's greatest hits on my hour long morning commute, and eventually it was just natural to bend the notes at the right time. My advice is to look for Jason Ricci on YouTube. He has hundreds or thousands of videos on beginner to advanced subjects. He is a weird dude, but I've never known a better teacher.

Damn language barrier, I thought this was about the accordion

This is the best explanation I've found of the mechanics of pitch bending https://youtu.be/Fp-GxEaChr0?si=-E9uDTQx51gtnd9C

Essentially, match the size of the resonance chamber in your mouth to the note you're trying to bend to. This is different for every note you bend. You can find the right size by making "hissing" noises while breathing in (without harmonica) and matching the pitch.