I spent a lot of time this long weekend making improvements to my perfect pitch training app: https://pganssle.github.io/cim/
I'm pretty happy with how it's shaping up. My son has been using it 4-5 times per day (the sessions are frequent but short), and it's kind of amazing to see how good he is at identifying chords.
It is all open source and designed to be easy to fork and deploy if desired: https://github.com/pganssle/cim
If you are good at web design or music theory I'd be very happy to see contributions (including just giving feedback)! Doesn't take much to be better at those things than me... 😛 ([Exhibit A](https://github.com/pganssle/cim/issues/9) 😅)
@pganssle tried this out, and it was fun! Relative pitch is enough to do it though? Bit skeptical of the "absolute pitch" claims, bit it seems useful and fun for relative pitch
@marcogorelli I think for adults there are established techniques for improved ear training. I am not sure if simply doing those as often as we do the chord identification method trainer would give a similar probability of attaining perfect pitch. It seems like kids with early exposure to music are pretty significantly more likely to get perfect pitch and have the kind of intuitive relationship to music that a lot of musicians have, so it might be that pretty much any sort of ear training will work when you start this young.