I also find that it is very important to know how the music is supposed to sound. Often, when I don't know the 'tune' of what I am playing, I also find it hard to get the intonation right. Maybe its just me, but . . .

Thank you for bringing this topic. A lot of good highlights especially about finding a pattern in myself mistakes. There've been few months since I asked that question and I can share what helped myself with intonation practice. Even if I see a long way ahead to get an "acceptable" intonation in middle registers of the bass. First of all - repetition and consistency. If I have only 30 minutes for double bass practice during some day I will dedicate this to intonation. If I have 2 hours, then around 40 minutes will be about intonation and rest for other stuff. Of course, intonation practice also brings element of bowing practice (getting good, full sound) and fretboard knowledge (finding scale notes and intervals on the instrument) Also practicing singing intervals, scales and chords with some "pitch fixed" instrument (like the bass guitar or piano) helped exercise my ear, so I have a better understanding what I am about to play before I play it. So more often I know more or less what pitch I am aiming for instead of just "shooting" and hoping, that I will land on correct spot.

Follow-up question with intonation, are there any intervallic exercises you recommend for working on your ear with the bass? So if have to correct your intonation (let's say a string might fall slightly out in between tunes/pieces) you might do it faster. This is one of things I find useful, but not a ton of study materials out there on. (Thought this might be a good topic for brainstorming.)

I'm starting to try to become less dependent on my tuner. Growing up playing bass guitar, I would tune the instrument, and that would be all of the intonation I have to worry about. Learning upright, I sometimes have people telling me I need to work on my intonation. Most of the time I'm being judged by people who don't play intonation sensitive instruments, so I don't know if they're being overly critical of those 2-3 notes that I quickly corrected, or many others I didn't hear myself. Thus I'm working on tuning my instruments by ear rather than by tuner so that I can better learn how to hear intonation. Speaking of this concept; something I've found with my playing is that I'm starting to hear a difference between equal temperament and just intonation. I've been wondering if this is contributing to my intonation problems as my ear wants to tune the pitches to the just intonation system, but musicians who play equal temperament (like piano) consider it wrong because they're use to that. I'm beginning to hear pianos out of tune.

My teacher says playing in tune is a matter of hearing it clearly first. It comes from the ear first.