My goal when I decided to start relearning piano was to become the most rounded musician that I could be, meaning I don't care about playing the most technically advanced pieces, but could play with some level of technical proficiency, could improvise, could sight read somewhat well, and most importantly, could hear music well.
To this end, I built myself my own little ear trainer on this website (you can access it here Ear Trainer). The first iteration of this tool had no actual UI to speak of, I'd just sit in front of my piano, and pressed different keys on my computer keyboard to trigger different tests. On top of this, all configuration was done through me editing code. It was something that became very handy for me, but almost certainly not for anyone else.
When I was setting up this website I decided that I'd include a v2 of the ear trainer on the site, that way anyone could easily access it if they wanted to. It has a full UI, multiple tests covering intervals, scale degrees, melodies & chord progressions, and each of them can be pretty thoroughly configured too!
I must admit, ear training is a pretty slow burn when it comes to its actual usefulness. The first few months I was doing it, I was definitely progressing at passing the tests, but struggled to actually translate that progress onto real-world songs. As I kept going though, I started noticing that when humming a tune in the shower, I was able to start picking out notes from it. I started being able to actually figure out whole melodies in my head. When I got out of the shower I'd then run over to my piano to check if I was correct.
This aspect of being able to actually apply your ear training to real music is so important, because real music is generally so much more complex than the examples you'll practice with on ear trainers. They're also so much more interesting and so can actually keep you motivated to carry on. Having a good ear trainer is still really important though, since if you find you're struggling with particular things then you can isolate just those areas to work on.
As my ear got better, I began transcribing songs, a few of which are listed here. I don't know why exactly, but I have a real preference for doing the stupid frivolous songs rather than anything particularly moving or serious.
Final Fantasy 7 - Barret's Theme
Funeral For A Friend - Roses For The Dead
Anyway, try out the ear trainer here, let me know if you have any suggestions for ways to improve it, and hopefully have fun with it!