As someone who aspires to be a musician I know the importance of a good musical ear, but it is something I have not specifically worked on much. I remember at school a music teacher would test us on picking out intervals, but I was not particularly good at it. Since then I have played a lot of music, mostly on guitar, and find I can pick out some tunes fairly well just by feel. Generally if you can work out what scale a tune uses it is not too hard. I tend to do this by 'feel' rather than instinctively knowing that intervals are involved.
Image from Wikimedia
I have decided to make more of a dedicated effort to improving this aspect of my musical abilities. I do not expect to achieve perfect pitch. That is a fairly rare ability where people can hear a note in isolation and know it is a C, for example. If you do not develop this in early childhood then it seems you are unlikely to be able to learn it later. Relative pitch is being able to hear the difference between notes and can be as useful most of the time.
The internet is full of material that could be useful. I have been looking at various videos on Youtube and eventually found The Musical Ear from a British guy called Julian Bradley. His angle is that you work out tunes relative to one particular key rather than the actual key of a song. I think the idea is that you get really used to that key. Later you can adapt to other keys.
You can find with some teachers that they say you have to learn all the possible intervals (12 within an octave), whereas Julian concentrates on those that are most commonly used in actual music. He points out that a lot of songs use patterns of just a few notes, e.g. root, minor third, fourth and fifth. If you can learn to hear those patterns then it makes it easier to play the tune.
He offers some further lessons if you subscribe to his email list on his site. I suspect this is building to offering a paid course and there are mentions of that in some reviews on his site. I have found some other music teachers are also quite cagey about what they charge. Some of them try to sell you various other things with 'limited time discounts' before you have even started the first paid course and that can put me off. I will see where he takes it.
In the meantime I will try to fit some more ear training practice into my day. He suggests some intervals you should work on and so I will try doing a different one each day over a week. I am starting with the whole tone by playing notes on my guitar and trying to sing the other. This is pretty easy going up as they will be the first two notes of a scale (do, re). Going down is a little harder and so I need to really work on this. You really have to feel the notes as this is not something you can see or touch.
Although I have played music for decades I have not spent that much time studying how music actually works. That is not essential to being a musician, but I feel it can add to the experience. I do like to analyse things generally.
Talking of analysing, this series on Netflix is interesting as it dives into how songs are created. I also want to improve my songwriting, so I hope to pick up some tips.