Ask HN: What does it feel like to master playing an instrument by ear?

I grew up monolingual, and only acquired a second language in adulthood. When I was younger I would ask people what it was like to speak two languages, what was going on in their heads, what did it feel like and so on. It seemed like magic.

Then I moved to another country and slowly, over the years I picked up another language. Each individual step felt small. Nothing magical was happening each time. But sooner or later I could speak another language fluently. Somewhat disappointingly, there was no magic in my head. It just felt 'normal'.

I suspect this is what having a great ear for music feels like. You're either born with it or build it through many many years of practice. Because of this, it never seems particularly special to the holder.

(An aside: I played trumpet for 4 years in high school and still cannot tell if a song is in a major key or minor key, and cannot tune an instrument so if anyone has the secret to gaining a musical ear I'm 'all ears'.)

One is the ability to hear and predict, Markov-chain style, the chord progressions in a song. This actually isn't very difficult, once you realize that 1) all songs make use of exactly the same handful of existing chord-to-chord transitions, just shifted depending on the root chord (key) the sheet music is written in, 2) some chord transitions are vastly more common than others, and 3) each transition has a distinct feel, which your brain soon learns to appreciate with an intuition similar to that you have for language.

Thus, it helps to re-write each piece of sheet music into C before you play it ("normalization", if you will), so you can see and hear the essence of e.g. C→G across the context of different pieces. Later, go around the circle of fifths, so you can see the patterns reappear in keys other than C. Music theory textbooks use tables of Roman numerals for this, but those only make sense to people who already have the intuition anyway. But there are good videos on this, like https://www.youtube.com/channel/UC8qv5hZppyGQbe9laVKwg3w.

Playing chords by ear is a very satisfying feeling, because it gives you the illusion that you're 80% there with 20% of the effort. It also translates easily to other instruments.

Second is the ability to hear and play back melodies. This comes with practice. Trial and error, hit and miss ... until your miss rate goes down, which it will, slowly, over time, asymptotically approaching zero. As you practice your intuition for chords, however, you will soon know what certain intervals (especially 3, 4, 5) sound like, and that will often help you find the right next note. When you hit a plateau, read up on different types of scales – knowing "this part of the melody is mixolydian" will prune the search tree for you.

Being able to pick out the right note without thinking will turn the instrument into an extension of yourself, just as you sing or whistle without thinking. However, you may well be a proficient amateur harmonium player long before you can reproduce any complex melody completely error-free, so I don't know that it's something worth obsessing about.

Third is the ability to play more than just simple triads and monophonic melodies, but to add patterns and rhythms and chord inversions and "crunchy" notes (sus, dim, maj, 6, 9, 13, etc.) and improvisations on the melody. Those aren't self-contained skills, but rather a repertoire of tricks that you acquire as you play and analyze other people's music, and there are lots of textbooks and videos on them. Those don't do that much for your perceived level of "fluency", but they do make you feel "eloquent" and they're great for your ego.

I had some guitar lessons as a teenager, covering a mix of technique, vocabulary and theory. But I was not academically schooled in music.

There are two things that help develop this skill I think, extrapolating from my own experience:

One is, when learning a piece I find it useful to hum or sing the notes I am trying to learn. i.e. play back a bit of the recording, then pause and hum it to myself while finding the notes on the instrument. It sounds trivial and obvious, but it helps build the connections and to hear the music in your head.

I think part of being able to do it involves "having the instrument in your head".

The second tip is then to follow on from the first but do it without a recording and without the instrument in your hands. Hum the notes to yourself and try to imagine where they are on the "instrument in your head". If you don't already know the key just choose an arbitrary one. This helps two things - develop the instrument in your head, also a sense of relative pitch (intervals) between the individual notes in sequence, and also between each note and the key centre.

I distinctly remember as a teenager this was something I liked to do while on my way to and from school - hearing back a guitar solo in my head and trying to play it, in my head. And then when I got home I could try it out on the instrument and see how close I was.