Learning music theory helps a ton for this.
Yes, I've played with guys that can hear something and play it, but have no idea of the theory behind it.

I've also worked with people that understand theory and it makes learning (and writing) a song so much easier.

First learn the intervals; what does a root-5-root sound like (easy)
Then root-4-root (again easy)
Then minor 3rd root (again easy)
Then move on, there really aren't that many.
https://www.justinguitar.com/guitar-lessons/song-references-for-interval-ear-training-et-099

Once you can hear intervals, the bass part becomes easier.
Once you learn theory the rest makes sense, and it's based on the same intervals.

We only have 12 notes to play with.
It's like learning a new language but with only twelve characters. smile

When I first heard Al Stewart's Year of the Cat I just had to learn those chords and why they worked like they did .. then I listened to the next song on the album (yeah it was back in the vinyl days) and had to learn On the Border (the 9ths, and the same melodic line working over different chords intrigued me).

Have fun while doing it, but really worth learning the theory behind it all.

I do not work here, but the benefits are still awesome
Make your sound your own!