When I left school and began to apply what I'd learned on upright to the bass guitar (well over 30 years ago now), I was taught that in general it's desirable to play notes in the lowest possible position as this means using a longer, thinner string rather than a shorter, thicker one, hence cleaner tone. For example, to play the lowest B on a 4 string, it's generally better to play 2nd fret on the A string than 7th fret E string. Or, to really exaggerate the tonal difference, compare 15th fret E to an open G! I should say there were some exceptions to this - such as where it would make fingering very difficult (disco style alternating octave 8ths in Eb, for example) or where it would make damping open strings harder (I do notice a lot of people avoiding open strings for this very reason, which always seems a pity to me), or where a player is trying to avoid too much of a stretch. So, it was intended generally rather than in every single instance. To give a specific example of when it would apply, think of the classic root - major 3rd - fifth - sixth - octave - sixth - fifth - major 3rd pattern in, say, Db. This would be better played from 4th fret on the A string than 9th fret E string according to the guideline. I don't seem to see this mentioned these days. Why do you think that is? Is it something that wasn't valid 30 years ago and has died, or was it good advice that gets overlooked for some reason nowadays? Or are people still recommending this and I've missed it? I don't think the latter is true universally because watching Youtube and so on I do seem to see a lot of players playing lines in higher positions than I would choose to use myself. I'll see if I can find some vids to post if folks are interested.